Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers
We fit the size distribution of liquid-ordered (Lo) domains measured from fluorescence images of model cytoplasmic myelin monolayers with an equilibrium thermodynamic expression that includes the competing effects of line tension, λ, dipole density difference, Δm, and the mixing entropy. From these...
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| Format: | Article |
| Language: | en_US |
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National Academy of Sciences (U.S.)
2012
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| Online Access: | http://hdl.handle.net/1721.1/69943 |
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| author | Lee, Dong Woog Min, Younjin Dhar, Prajnaparamita Ramachandran, Arun Israelachvili, Jacob N. Zasadzinski, Joseph A. |
| author2 | Massachusetts Institute of Technology. Department of Chemical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Chemical Engineering Lee, Dong Woog Min, Younjin Dhar, Prajnaparamita Ramachandran, Arun Israelachvili, Jacob N. Zasadzinski, Joseph A. |
| author_sort | Lee, Dong Woog |
| collection | MIT |
| description | We fit the size distribution of liquid-ordered (Lo) domains measured from fluorescence images of model cytoplasmic myelin monolayers with an equilibrium thermodynamic expression that includes the competing effects of line tension, λ, dipole density difference, Δm, and the mixing entropy. From these fits, we extract the line tension, λ, and dipole density difference, Δm, between the Lo and liquid-disordered (Ld) phases. Both λ and Δm decrease with increasing surface pressure, Graphic, although λ/Δm2 remains roughly constant as the monolayer approaches the miscibility surface pressure. As a result, the mean domain size changed little with surface pressure, although the polydispersity increased significantly. The most probable domain radius was significantly smaller than that predicted by the energy alone, showing that the mixing entropy promotes a greater number of smaller domains. Our results also explain why domain shapes are stable; at equilibrium, only a small fraction of the domains are large enough to undergo theoretically predicted shape fluctuations. Monolayers based on the composition of myelin from animals with experimental allergic encephalomyelitis had slightly lower values of λ and Δm, and a higher area fraction of domains, than control monolayers at all Graphic. While it is premature to generalize these results to myelin bilayers, our results show that the domain distribution in myelin may be an equilibrium effect and that subtle changes in surface pressure and composition can alter the distribution of material in the monolayer, which will likely also alter the interactions between monolayers important to the adhesion of the myelin sheath. |
| first_indexed | 2024-09-23T11:56:14Z |
| format | Article |
| id | mit-1721.1/69943 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T11:56:14Z |
| publishDate | 2012 |
| publisher | National Academy of Sciences (U.S.) |
| record_format | dspace |
| spelling | mit-1721.1/699432022-10-01T07:04:32Z Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers Lee, Dong Woog Min, Younjin Dhar, Prajnaparamita Ramachandran, Arun Israelachvili, Jacob N. Zasadzinski, Joseph A. Massachusetts Institute of Technology. Department of Chemical Engineering Min, Younjin Min, Younjin We fit the size distribution of liquid-ordered (Lo) domains measured from fluorescence images of model cytoplasmic myelin monolayers with an equilibrium thermodynamic expression that includes the competing effects of line tension, λ, dipole density difference, Δm, and the mixing entropy. From these fits, we extract the line tension, λ, and dipole density difference, Δm, between the Lo and liquid-disordered (Ld) phases. Both λ and Δm decrease with increasing surface pressure, Graphic, although λ/Δm2 remains roughly constant as the monolayer approaches the miscibility surface pressure. As a result, the mean domain size changed little with surface pressure, although the polydispersity increased significantly. The most probable domain radius was significantly smaller than that predicted by the energy alone, showing that the mixing entropy promotes a greater number of smaller domains. Our results also explain why domain shapes are stable; at equilibrium, only a small fraction of the domains are large enough to undergo theoretically predicted shape fluctuations. Monolayers based on the composition of myelin from animals with experimental allergic encephalomyelitis had slightly lower values of λ and Δm, and a higher area fraction of domains, than control monolayers at all Graphic. While it is premature to generalize these results to myelin bilayers, our results show that the domain distribution in myelin may be an equilibrium effect and that subtle changes in surface pressure and composition can alter the distribution of material in the monolayer, which will likely also alter the interactions between monolayers important to the adhesion of the myelin sheath. National Institutes of Health (U.S.) (Grant GM076709) National Institutes of Health (U.S.) (Grant HL051177) 2012-04-05T13:56:59Z 2012-04-05T13:56:59Z 2011-06 2011-02 Article http://purl.org/eprint/type/JournalArticle 0027-8424 1091-6490 http://hdl.handle.net/1721.1/69943 Lee, D. W. et al. “Relating Domain Size Distribution to Line Tension and Molecular Dipole Density in Model Cytoplasmic Myelin Lipid Monolayers.” Proceedings of the National Academy of Sciences 108.23 (2011): 9425–9430. en_US http://dx.doi.org/10.1073/pnas.1106368108 Proceedings of the National Academy of Sciences of the United States of America Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf National Academy of Sciences (U.S.) PNAS |
| spellingShingle | Lee, Dong Woog Min, Younjin Dhar, Prajnaparamita Ramachandran, Arun Israelachvili, Jacob N. Zasadzinski, Joseph A. Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers |
| title | Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers |
| title_full | Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers |
| title_fullStr | Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers |
| title_full_unstemmed | Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers |
| title_short | Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers |
| title_sort | relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers |
| url | http://hdl.handle.net/1721.1/69943 |
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