Coarse-Grained Model for PEGylated Lipids: Effect of PEGylation on the Size and Shape of Self-Assembled Structures.
Summary of "Coarse-Grained Model for PEGylated Lipids: Effect of PEGylation on the Size and Shape of Self-Assembled Structures."
Self-assembly of polyethylene glycol (PEG)-grafted lipids at different sizes and concentrations was simulated using the MARTINI coarse-grained (CG) force field. The interactions between CG PEG and CG dipalmitoylglycerophosphocholine (DPPC)-lipids were parametrized by matching densities of 19-mers of PEG and polyethylene oxide (PEO) grafted to the bilayer from all-atom simulations. Mixtures of lipids and PEG-grafted (M(w) = 550, 1250, and 2000) lipids in water self-assembled to liposomes, bicelles, and micelles at different ratios of lipids and PEGylated lipids. Average aggregate sizes decrease with increasing PEGylated-lipid concentration, in qualitative agreement with experiment. PEGylated lipids concentrate at the rims of bicelles, rather than at the planar surfaces; this also agrees with experiment, though the degree of segregation is less than that assumed in previous modeling of the experimental data. Charged lipids without PEG evenly distribute at the rim and planar surfaces of the bicelle. The average end-to-end distances of the PEG on the PEGylated lipids are comparable in liposomes, bicelles (edge or planar surface), and micelles and only slightly larger than for an isolated PEG in solution. The ability of PEGylated lipids to induce the membrane curvature by the bulky headgroup with larger PEG, and thereby modulate the phase behavior and size of lipid assemblies, arises from their relative concentration.
Affiliation
Department of Chemical Engineering, Dankook University, Yongin, 448-701, South Korea.
Journal Details
This article was published in the following journal.
Name: The journal of physical chemistry. B
ISSN: 1520-5207
Pages: 7830-7
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21618987
- DOI: http://dx.doi.org/10.1021/jp2020148
Medical and Biotech [MESH] Definitions
Eosinophils
Granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin.
Models, Statistical
Statistical formulations or analyses which, when applied to data and found to fit the data, are then used to verify the assumptions and parameters used in the analysis. Examples of statistical models are the linear model, binomial model, polynomial model, two-parameter model, etc.
Basophils
Granular leukocytes characterized by a relatively pale-staining, lobate nucleus and cytoplasm containing coarse dark-staining granules of variable size and stainable by basic dyes.
Lipolysis
The metabolic process of breaking down LIPIDS to release FREE FATTY ACIDS, the major oxidative fuel for the body. Lipolysis may involve dietary lipids in the DIGESTIVE TRACT, circulating lipids in the BLOOD, and stored lipids in the ADIPOSE TISSUE or the LIVER. A number of enzymes are involved in such lipid hydrolysis, such as LIPASE and LIPOPROTEIN LIPASE from various tissues.
Membrane Lipids
Lipids, predominantly phospholipids, cholesterol and small amounts of glycolipids found in membranes including cellular and intracellular membranes. These lipids may be arranged in bilayers in the membranes with integral proteins between the layers and peripheral proteins attached to the outside. Membrane lipids are required for active transport, several enzymatic activities and membrane formation.
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