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Polymorphic phase behavior of cardiolipin derivatives studied by coarse-grained molecular dynamics
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2007 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, Vol. 111, no 25, 7194-7200 p.Article in journal (Refereed) Published
Abstract [en]

Cardiolipin (CL) is a negatively charged four acyl chain lipid, associated with energy production in bacterial and mitochondrial membranes. Due to the shape of CL, negative curvatures of aggregates are favorable if the charges in the head group can be reduced. The phase polymorphism of CL, and of associated derivatives with 2, 3, 4, or 5 chains, has been determined previously and offers a model system in which micellar, lamellar, and inverse hexagonal phases can be observed. We present an extension to a previously established coarse-grained molecular dynamics model with the aim of reproducing the different CL phases with two adjustable parameters: the number of acyl chains and the effective head group charge. With molecular dynamics simulations of large lipid systems, we observed transitions between different phases on the nanosecond to microsecond time scale. Charge screening by high salt or low pH was successfully modeled by a reduction of phosphate charge, which led to the adoption of aggregates with more negative curvature. Although specific ion binding at the interface and other atomistic details are sacrificed in the coarse-grained model, we found that it captures general phase features over a large range of aggregate geometries.

Place, publisher, year, edition, pages
Whashington: AMER CHEMICAL SOC , 2007. Vol. 111, no 25, 7194-7200 p.
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-19666DOI: 10.1021/jp071954fISI: 000247435700032OAI: oai:DiVA.org:su-19666DiVA: diva2:186190
Available from: 2007-11-28 Created: 2007-11-28 Last updated: 2010-03-17Bibliographically 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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