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Mechanical properties of coarse grained bilayers formed by cardiolipin and zwitterionic lipids
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
2010 (English)In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 6, no 5, 1638-1649 p.Article in journal (Refereed) Published
Abstract [en]

Lipid shape and charge are connected with the physical properties and biological function of membranes. Cardiolipin, a double phospholipid with four chains and the potential of changing its charge with pH, is crucially connected with mitochondrial inner membrane shape, and recent experiments suggest that local pH changes allow highly curved local geometries. Here, we use a coarse grained molecular dynamics model to investigate the mechanical properties of cardiolipin bilayers, systematically varying the headgroup charge and composition in mixtures with zwitterionic DOPC or DOPE. Low cardiolipin charge, corresponding to low pH, was found to induce bending moduli on the order of kBT, and curved microdomains. On the length scale investigated, in contrast to continuum theoretical models, we found the area modulus and bending modulus to be inversely correlated for mixtures of cardiolipin and DOPC/DOPE, explainable by changes in the effective head group volume.

Place, publisher, year, edition, pages
2010. Vol. 6, no 5, 1638-1649 p.
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-37612DOI: 10.1021/ct900654eISI: 000277408500018OAI: oai:DiVA.org:su-37612DiVA: diva2:304020
Projects
Liquid Crystals and Membrane Models
Available from: 2010-03-16 Created: 2010-03-16 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Molecular Modeling of Cardiolipin
Open this publication in new window or tab >>Molecular Modeling of Cardiolipin
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biological membranes are assembled from many different lipids. Our understanding of membrane function and morphology is dependent on linking the properties of the lipids to the properties of the membranes. In the inner mitochondrial membrane, one of the main lipids is cardiolipin, which is involved in the formation of high curvature tubular regions. In this thesis a series of molecular models of cardiolipin is presented, with the aim of providing a bottom-up understanding for its influence on model and biological membranes. The models allow detailed control over the headgroup charge and the chain volumes, which experimentally have shown to be important for the packing, mechanical, and electrostatic properties of membranes.To achieve these aims, three levels of detail were used: i) quantum chemical calculations for the cardiolipin headgroup, ii) atomistic united atom molecular dynamics simulations for cardiolipin and phosphatidylcholine lipid mixtures, and iii) coarse grained molecular dynamics simulations for larger lipid systems, including phase transitions between the micellar, lamellar, and inverse hexagonal phases, as well as mixtures of cardiolipin with zwitterionic lipids. These models are presented in the context of various experiments on cardiolipin systems done by others, and some basic theory of electrostatics and mechanics of membranes are discussed.The simple coarse grained model gave lipid phase preferences in agreement with experimental data. Relatively small amounts of partially neutralized cardiolipin molecules introduced mechanical instability in phosphatidylcholine bilayers, and showed some evidence of domain formation due to curvature frustration. The small effective headgroup volume of cardiolipin induced order in the hydrocarbon chains, partly due to strong sodium ion binding. Different types of intramolecular hydrogen bond networks in cardiolipin were described, and proton transfer between the phosphate groups within a cardiolipin molecule was estimated to have a 4-5 kcal/mol barrier. Such transfer might play a role in the surface conduction of protons at the inner mitochondrial membrane.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2010. 97 p.
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-37613 (URN)978-91-7447-024-6 (ISBN)
Public defence
2010-04-16, Magnelisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.Available from: 2010-03-25 Created: 2010-03-16 Last updated: 2010-03-17Bibliographically approved

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