| 1. |
- Akesson, Anna, et al.
(författare)
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Composition and structure of mixed phospholipid supported bilayers formed by POPC and DPPC
- 2012
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 8:20, s. 5658-5665
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a systematic study of the morphology and composition of supported lipid bilayers (SLBs) formed by vesicle fusion using a wide variety of surface sensitive techniques that give information about the lateral as well as vertical structure and bilayer fluidity. SLBs of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) mixtures at five different bulk vesicle compositions were formed in such a way that the phase separation boundaries were crossed. For all compositions studied, the SLBs were systematically enriched with POPC compared to the nominal vesicle composition. Nevertheless, gel-fluid domain coexistence was observed for SLB compositions in which phase separation was expected based on the bulk phase diagram. The probable causes for the compositional difference in the SLBs are discussed in terms of the phase behaviour of the mixture and its effect on the membrane formation process by vesicle fusion.
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| 2. |
- Akesson, Anna, et al.
(författare)
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The effect of PAMAM G6 dendrimers on the structure of lipid vesicles
- 2010
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 12:38, s. 12267-12272
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Tidskriftsartikel (refereegranskat)abstract
- Dendrimers are polymers with unique properties that make them promising in a variety of applications such as potential drug and gene delivery systems. PAMAM dendrimers, in particular, have been widely investigated and are efficiently translocated into the cell. The mechanism of translocation, however, is still unknown. Recently it was proposed that PAMAM dendrimers are able to open holes in lipid bilayers by stealing lipid from the bilayer and forming "dendrisomes''. The present work intends to contribute in the clarification of this question: why are dendrimers able to translocate into the cell? We create simple models for cell membranes by using small lipid vesicles that present a single lipid phase at physiologically relevant conditions. We then follow the effect that dendrimers have on the structure of the vesicles by using a combination of various techniques: dynamic light scattering, cryo-TEM and small angle X-ray scattering. We discuss our results with respect to the previous findings and reflect on their possible implications for real translocation in living cells.
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| 3. |
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| 4. |
- Bertram, Nicolas, et al.
(författare)
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Nanodisc films for membrane protein studies by neutron reflection : Effect of the protein scaffold choice
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:30, s. 8386-8391
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Tidskriftsartikel (refereegranskat)abstract
- Nanodisc films are a promising approach to study the equilibrium conformation of membrane bound proteins in native-like environment. Here we compare nanodisc formation for NADPH-dependent cytochrome P450 oxidoreductase (POR) using two different scaffold proteins, MSP1D1 and MSP1E3D1. Despite the increased stability of POR loaded MSP1E3D1 based nanodiscs in comparison to MSP1D1 based nanodiscs, neutron reflection at the silicon–solution interface showed that POR loaded MSP1E3D1 based nanodisc films had poor surface coverage. This was the case, even when incubation was carried out under conditions that typically gave high coverage for empty nanodiscs. The low surface coverage affects the embedded POR coverage in the nanodisc film and limits the structural information that can be extracted from membrane bound proteins within them. Thus, nanodisc reconstitution on the smaller scaffold proteins is necessary for structural studies of membrane bound proteins in nanodisc films.
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| 5. |
- Brennich, Martha, et al.
(författare)
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Nanoparticle Characterization Methods : Applications of Synchrotron and Neutron Radiation
- 2016
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Ingår i: Pharmaceutical Nanotechnology. - Weinheim, Germany : John Wiley & Sons. - 9783527340545 - 9783527800681 ; , s. 157-174
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Bokkapitel (refereegranskat)abstract
- The characterization of materials at the atomic-, nano-, and microscales is of crucial importance in understanding and then tailoring their macroscale properties and function for end-use applications and for effective modern cradle-to-reuse materials cycling. Synchrotron light, as well as the complementary neutron beams, offer exquisite microscopy probes to look into the heart of materials. This chapter presents some examples of pharma-oriented nanoparticle characterization highlighting the possibilities of synchrotron light and neutron beams. Small-angle X-ray scattering (SAXS) is a well-established technique to probe nanoscale structures. SAXS can also deliver valuable information on the structure of self-assembled nanovectors, such as liposomes, which are recognized as efficient platforms for drug delivery. Future developments for neutron characterization will be driven in parallel with instrumental developments at existing sources and future facilities such as the European Spallation Source (ESS) being built in Sweden.
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| 6. |
- Browning, Kathryn L., et al.
(författare)
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Effect of bilayer charge on lipoprotein lipid exchange
- 2018
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Ingår i: Colloids and Surfaces B. - : ELSEVIER SCIENCE BV. - 0927-7765 .- 1873-4367. ; 168, s. 117-125
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Tidskriftsartikel (refereegranskat)abstract
- Lipoproteins play a key role in the onset and development of atherosclerosis, the formation of lipid plaques at blood vessel walls. The plaque formation, as well as subsequent calcification, involves not only endothelial cells but also connective tissue, and is closely related to a wide range of cardiovascular syndromes, that together constitute the number one cause of death in the Western World. High (HDL) and low (LDL) density lipoproteins are of particular interest in relation to atherosclerosis, due to their protective and harmful effects, respectively. In an effort to elucidate the molecular mechanisms underlying this, and to identify factors determining lipid deposition and exchange at lipid membranes, we here employ neutron reflection (NR) and quartz crystal microbalance with dissipation (QCM-D) to study the effect of membrane charge on lipoprotein deposition and lipid exchange. Dimyristoylphosphatidylcholine (DMPC) bilayers containing varying amounts of negatively charged dimyristoylphosphatidylserine (DMPS) were used to vary membrane charge. It was found that the amount of hydrogenous material deposited from either HDL or LDL to the bilayer depends only weakly on membrane charge density. In contrast, increasing membrane charge resulted in an increase in the amount of lipids removed from the supported lipid bilayer, an effect particularly pronounced for LDL. The latter effects are in line with previously reported observations on atherosclerotic plaque prone regions of long-term hyperlipidaemia and type 2 diabetic patients, and may also provide some molecular clues into the relation between oxidative stress and atherosclerosis.
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| 7. |
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| 8. |
- Browning, T. K., et al.
(författare)
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Human lipoproteins at model cell membranes : Role of the lipoprotein class on lipid dynamics
- 2017
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- High and low density lipoproteins (HDL and LDL) are thought to play vital roles in the onset and development of atherosclerosis; the biggest killer in the western world. Key issues of initial lipoprotein (LP) interactions at cellular membranes need to be addressed including LP deposition and lipid exchange. Here we present a protocol for monitoring the in situ kinetics of lipoprotein deposition and lipid exchange/removal at model cellular membranes using the non-invasive, surface sensitive methods of neutron reflection and quartz crystal microbalance with dissipation. For neutron reflection, lipid exchange and lipid removal can be distinguished thanks to the combined use of hydrogenated and tail-deuterated lipids. Both HDL and LDL remove lipids from the bilayer and deposit hydrogenated material into the lipid bilayer, however, the extent of removal and exchange depends on LP type. These results support the notion of HDL acting as the ‘good’ cholesterol, removing lipid material from lipid-loaded cells, whereas LDL acts as the ‘bad’ cholesterol, depositing lipid material into the vascular wall.
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| 9. |
- Cárdenas, Marité, et al.
(författare)
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Cellulose Nanofibers for Biomedical Applications
- 2016
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Ingår i: Biopolymers for Medical Applications. - Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742 : CRC Press. - 9781498744966 ; , s. 213-232
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Bokkapitel (refereegranskat)abstract
- The creation of materials exploiting molecules from renewable resources and green processing routes in order to minimize contamination of the environment with toxic solvents and starting components, is an important step towards a sustainable society, and sustainable development is critical in all technological fields including biomedical engineering. In this context, the polysaccharides are an important family of molecules, as they can be derived from numerous natural sources including plants, bacteria, insects, animals, and also from by-products/waste-materials obtained from agricultural or fishery activities. Also, polysaccharides are biodegradable and can be broken down by common microorganisms found on land or in water. In nature, polysaccharides can be composed of one type of repeating unit (homopolysaccharides; starch and cellulose) or two or more types of repeating monomer (heteropolysaccharides; pectin, alginate). But despite using only a few basic building blocks, many unique and complex molecular structures with specific features and functions are assembled giving rise to a plethora of diverse carbohydrates. Some of the polysaccharides are classified as polyelectrolytes, and these are either negatively or positively charged. The intrinsic properties of such ionic polysaccharides are used in material science to produce stimuli-responsive materials where external stimuli (pH, ionic strength, and temperature) trigger, for example, a mechanical response in the material or a swelling mechanism that can be exploited in drug delivery. In addition to conventional polysaccharides, advanced genetic engineering also opens up the possibility for new, innovative, and structurally designed macromolecules with specific chemical and physical properties, allowing for better material structure-property control. Natural polysaccharides are typically biocompatible, possibly bioadhesive, and generally recognized as safe (GRAS) and, in conclusion, they are attractive materials to use in biomedical applications.
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| 10. |
- Cárdenas, Marité, et al.
(författare)
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DNA and cationic surfactant complexes at hydrophilic surfaces. An ellipsometry and surface force study
- 2004
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:20, s. 8597-8603
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption and formation of DNA and cationic surfactant complexes at the silica-aqueous interface have been studied by ellipsometry. The interaction between the DNA-surfactant complexes at the mica-aqueous interface has been determined by the interferometric surface force apparatus. Adsorption was as expected not observed on negatively charged hydrophilic surfaces for DNA and when DNA-cationic surfactant complexes were negatively charged. However, adsorption was observed when there is an excess of cationic surfactant, just below the point of phase separation. The adsorption process requires hours to reach steady state. The adsorbed layer thickness is large at low surface coverage but becomes more compact and thinner at high coverage. A long-range repulsive force was observed between adsorbed layers of DNA-cationic surfactant complexes, which was suggested to be of both electrostatic and steric origin. The forces were found to be dependent on the equilibration time and the experimental pathway.
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