Steven O. Nielsen Department of Chemistry University of Texas at Dallas
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Lipid bilayer energetics and deformations probed by molecular dynamics computer simulations Steven O. Nielsen Department of Chemistry University of Texas at Dallas 1
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Lipid bilayer energetics and deformations probed by molecular dynamics computer simulations. Steven O. Nielsen Department of Chemistry University of Texas at Dallas. 1. Air/water interface in the lung. ~300 million alveoli in the adult lung. Harishchandra et al. - PowerPoint PPT Presentation
Transcript of Steven O. Nielsen Department of Chemistry University of Texas at Dallas
Lipid bilayer energetics and deformations probed by molecular dynamics computer simulations
Steven O. NielsenDepartment of Chemistry
University of Texas at Dallas1
Harishchandra et al. J. R. Soc. Interface, 7, S15–S26, 2010
Air/water interface in the lung
lipid monolayer
lipid bilayer
lipid bilayer
lipid bilayer
~300 million alveoli in the adult lung
One of the most important functions of the lung surfactant monolayer is to form the first line of defense against inhaled aerosols such as nanoparticles.
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---- monolayer ---- bilayer water to lipid ΔG
compress to expand back to0.40 nm2 / Lipid 0.63 nm2 / Lipid
C60
C540 C540
C60
Use a hollow shell (continuum) model
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Water vacuum transfer free energy of fullerenes
fullerene – LJ interaction
Spherical fullerenes have a range of sizesC60 C540
R = 10.5 ÅR = 3.5 Å
• Giant fullerenes found in nano-onions
Carbon 33, 989 (1995)
Particle location in DOPC lipid bilayer
6C60 C80 C240 C320 C540
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Aggregation Behavior in DOPCCan measure aggregation propensity as a function
of size using the solvation free energy method
R= 1.8 Å R= 2.0 Å
R= 2.5 Å R= 10 Å
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Bending rigidity measurement from the response (force) of a deformed membrane
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Estimated bending rigidity κ from of a DMPC bilayer as a function of the membrane size, L.
S. Kawamoto, T. Nakamura, S. Nielsen, and W. Shinoda, J. Chem. Phys. 139 034108 (2013).
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Lipid Polymorphism: Free Energy Analysis of Vesicle-to-Bicelle Transformation
Fromherz, Chem. Phys. Lett. 94, 259 (1983)edge energy
curvature energy
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Lipid Polymorphism: Free Energy Analysis of Vesicle-to-Bicelle Transformation
Measure the response (force) due to a cone potential that “wedges” open the vesicle.
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After a certain cone angle the transformation becomes spontaneous
W. Shinoda, T. Nakamura, and S. Nielsen,Soft Matter 7 9012-9020 (2011).
The problem is that the chosen reaction coordinate is flawed. It would be nice if we didn’t need to use a path !!
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14Partay et al, J. Phys. Chem. B (2010), 114, 10502.
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Acknowledgements
External CollaboratorsRussell DeVane (Procter & Gamble)
Chi-cheng Chiu
FundingSRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing
Nielsen Lab members
Udayana RanatungaAmir NasrabadiBlake Wilson
Wataru Shinoda (Nagoya U., Japan)
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Coarse Graining
Dipalmitoylphosphatidylcholine (DPPC)
• Coarse-Grain (CG) MD : – reduced number of particles– larger system, longer simulation time
• CG force field developed by Shinoda et al. • Parameterized against experimental and
atomistic simulation data– Surface tension– Transfer free energy –Membrane structural data
W. Shinoda et al. J. Phys. Chem. B 114, pp 6836–6849 (2010)
The question of the dispersion and subsequent potency for CNT to form aggregates … is often proposed as an important determinant of their biological effects.
, Boczkowski et al.
One common thread that emerges: toxicity in vivo is modulated by the aggregation of the nanomaterial.
, Trpkovic et al.
…conclude that the differences in cytotoxic potency and underlying mechanisms displayed by various fullerene preparations are mainly due to some physico-chemical characteristics, such as particle size (surface/volume ratio), surface charge, and aggregation properties.
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