The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Computational Modeling of Cationic Lipid Bilayers in Saline Solutions
Markus Miettinen
Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Information and Natural Sciences for public examination and debate in Auditorium K at the Aalto University School of Science and Technology (Espoo, Finland) on the 5th of June 2010 at 10 o'clock.
Dissertation in PDF format (ISBN 978-952-60-3194-1) [7622 KB]
Dissertation is also available in print (ISBN 978-952-60-3193-4)
Abstract
Based on computer simulations performed at single-molecule resolution, the effects of monovalent NaCl salt on cationic DMTAP/DMPC (dimyristoyltrimethylammoniumpropane/dimyristoylphosphatidylcholine) lipid bilayer systems are discussed. The monograph reviews, revises and expands the previously published work on how NaCl affects the structural and electrostatic [1] and the dynamic [2] properties of these systems.
The effects of NaCl depended qualitatively on the cationic DMTAP lipid fraction. When the fraction was low, NaCl had a notable effect of the structural properties of the bilayer, decreasing the area per lipid, increasing the tail order, reorienting the DMPC head groups, and increasing the average electrostatic potential difference over the head group region. At high DMTAP fraction there was scarcely an effect when NaCl was added.
The reason for this dichotomy was the ability of the Na+ ions to bind with the DMPC lipid carbonyl oxygens at low DMTAP fraction and to tie 2 to 4 DMPCs into a dynamic complex. At high DMTAP fraction the binding of Na+ was prevented by the high positive surface charge of the bilayer.
The lateral diffusion of Na+ ions within the carbonyl region had two qualitatively different modes. Na+ ions bound to a DMPC diffused very slowly, whereas the free Na+ ions traveled rapidly within the carbonyl region. The combined effect of the two motions appeared as Na+ ions hopping from one DMPC carbonyl oxygen to the next.
[1] A. A. Gurtovenko, M. S. Miettinen, M. Karttunen, and I. Vattulainen.
Effects of monovalent salt on cationic lipid membranes as revealed by molecular dynamics simulations.
J. Phys. Chem. B, 109: 21126–34 (2005).
[2] M. S. Miettinen, A. A. Gurtovenko, I. Vattulainen, and M. Karttunen.
Ion dynamics in cationic lipid bilayer systems in saline solutions.
J. Phys. Chem. B, 113: 9226–34 (2009).
Keywords: cationic lipid, dimyristoyltrimethylammoniumpropane, dimyristoylphosphatidylcholine, bilayer, sodium chloride, molecular dynamics, ion dynamics
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© 2010 Aalto University School of Science and Technology
Last update 2011-05-26