| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
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| 5. |
- 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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| 6. |
- 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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| 7. |
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| 8. |
- Falco, Cigdem Yucel, et al.
(författare)
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Chitosan-Dextran Sulfate Hydrogels as a Potential Carrier for Probiotics
- 2017
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 172, s. 175-183
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Tidskriftsartikel (refereegranskat)abstract
- Physical and chemical (crosslinked with genipin) hydrogels based on chitosan and dextran sulfate were developed and characterized as novel bio-materials suitable for probiotic encapsulation. The swelling of the hydrogels was dependent on the composition and weakly influenced by the pH of the media. The morphology analysis supports the swelling data showing distinct changes in microstructure depending on the composition. The viability and culturability tests showed approx. 3.6 log CFU/mL decrease of cells (L. acidophilus as model) incorporated into chemical hydrogels when compared to the number of viable native cells. However, the live/dead viability assay evidenced that a considerable amount of viable cells were still entrapped in the hydrogel network and therefore the viability is most likely underestimated. Overall, the developed systems are robust and their structure, rheology and swelling properties can be tuned by changing the blend ratio, thus constituting appealing bio-matrices for cell encapsulation.
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| 9. |
- Falco, Cigdem Yucel, et al.
(författare)
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Design of a potentially prebiotic and responsive encapsulation material for probiotic bacteria based on chitosan and sulfated beta-glucan
- 2017
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 487, s. 97-106
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Chitosan and sulfated oat beta-glucan are materials suitable to create a prebiotic coating for targeted delivery to gastrointestinal system, using the layer by layer technology. Experiment: Quartz crystal microbalance with dissipation (QCM-D), spectroscopic ellipsometry (SE) and atomic force microscopy (AFM) were used to assess the multilayer formation capacity and characterize the resulting coatings in terms of morphology and material properties such as structure and rigidity. The coating of colloidal materials was proven, specifically on L acidophilus bacteria as measured by changes in the bacterial suspension zeta potential. Viability of coated cells was shown using plate counting method. The coatings on solid surfaces were examined after exposure to mimics of gastrointestinal fluids and a commercially available beta-glucanase. Findings: Successful build-up of multilayers was confirmed with QCM-D and SE. Zeta potential values proved the coating of cells. There was 2 log CFU/mL decrease after coating cells with four alternating layers of chitosan and sulfated p-glucan when compared to viability of uncoated cells. The coatings were partially degraded after exposure to simulated intestinal fluid and restructured as a result of beta-glucanase treatment, mimicking enzymes present in the microflora of the human gut, but seemed to resist acidic gastric conditions. Therefore, coatings of chitosan and sulfated beta-glucan can potentially be exploited as carriers for probiotics and delicate nutraceuticals. (C) 2016 Elsevier Inc. All rights reserved.
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| 10. |
- Falco, Cigdem Yucel, et al.
(författare)
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Edible Foam Based on Pickering Effect of Probiotic Bacteria and Milk Proteins
- 2017
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Ingår i: Food Hydrocolloids. - : Elsevier. - 0268-005X .- 1873-7137. ; 70, s. 211-218
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Tidskriftsartikel (refereegranskat)abstract
- We report the preparation and characterization of aqueous Pickering foams using bio-particles constituted by lactic acid bacteria surface modified by oppositely charged milk proteins. Cell surface modification was shown by zeta potential measurements. Foams stabilized by bacterial Pickering bio-particles showed improved stability compared to purely milk protein stabilized foams. The stability of foams increased with the bacterial concentration whereas the foam volume (foamability) decreased. On the other hand, protein concentration was correlated with foamability but not with the foam stability. Optical and fluorescence microscopy revealed organized cell structures around and in between the air bubbles providing for an internal network that effectively stabilizes the foam. Therefore, entirely food grade stable foams can be produced by using modified health promoting bacterial cells and surface active milk proteins. Such Pickering systems can potentially be utilized in bottom up construction of more complex hierarchical food structures and further improve properties such as foam stability.
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