| 1. |
- Raj, Akanksha, et al.
(författare)
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Lubrication synergy : Mixture of hyaluronan and dipalmitoylphosphatidylcholine (DPPC) vesicles
- 2017
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 488, s. 225-233
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Tidskriftsartikel (refereegranskat)abstract
- Phospholipids and hyaluronan have been implied to fulfil important roles in synovial joint lubrication. Since both components are present in synovial fluid, self-assembly structures formed by them should also be present. We demonstrate by small angle X-ray scattering that hyaluronan associates with the outer shell of dipalmitoylphophatidylcholine (DPPC) vesicles in bulk solution. Further, we follow adsorption to silica from mixed hyaluronan/DPPC vesicle solution by Quartz Crystal Microbalance with Dissipation measurements. Atomic Force Microscope imaging visualises the adsorbed layer structure consisting of non-homogeneous phospholipid bilayer with hyaluronan/DPPC aggregates on top. The presence of these aggregates generates a long-range repulsive surface force as two such surfaces are brought together. However, the aggregates are easily deformed, partly rearranged into multilayer structures and partly removed from between the surfaces under high loads. These layers offer very low friction coefficient (<0.01), high load bearing capacity (≈23 MPa), and self-healing ability. Surface bound DPPC/hyaluronan aggregates provide a means for accumulation of lubricating DPPC molecules on sliding surfaces.
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| 2. |
- Wieland, D. C. Florian, et al.
(författare)
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Studying solutions at high shear rates : A dedicated microfluidics setup
- 2016
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Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography. - 0909-0495 .- 1600-5775. ; 23:2, s. 480-486
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Tidskriftsartikel (refereegranskat)abstract
- The development of a dedicated small-angle X-ray scattering setup for the investigation of complex fluids at different controlled shear conditions is reported. The setup utilizes a microfluidics chip with a narrowing channel. As a consequence, a shear gradient is generated within the channel and the effect of shear rate on structure and interactions is mapped spatially. In a first experiment small-angle X-ray scattering is utilized to investigate highly concentrated protein solutions up to a shear rate of 300000 s-1. These data demonstrate that equilibrium clusters of lysozyme are destabilized at high shear rates.
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| 3. |
- Zander, Thomas, et al.
(författare)
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Influence of high hydrostatic pressure on solid supported DPPC bilayers with hyaluronan in the presence of Ca2+ ions
- 2019
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Ingår i: Soft Matter. - : Royal Society of Chemistry. - 1744-683X .- 1744-6848. ; 15:36, s. 7295-7304
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Tidskriftsartikel (refereegranskat)abstract
- The molecular mechanisms responsible for outstanding lubrication of natural systems, like articular joints, have been the focus of scientific research for several decades. One essential aspect is the lubrication under pressure, where it is important to understand how the lubricating entities adapt under dynamic working conditions in order to fulfill their function. We made a structural investigation of a model system consisting of two of the molecules present at the cartilage interface, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and hyaluronan, at high hydrostatic pressure. Phospholipid layers are found at the cartilage surfaces and are able to considerably reduce friction. Their behavior under load and varied solution conditions is important as pressures of 180 bar are encountered during daily life activities. We focus on how divalent ions, like Ca2+, affect the interaction between DPPC and hyaluronan, as other investigations have indicated that calcium ions influence their interaction. It could be shown that already low amounts of Ca2+ strongly influence the interaction of hyaluronan with DPPC. Our results suggest that the calcium ions increase the amount of adsorbed hyaluronan indicating an increased electrostatic interaction. Most importantly, we observe a modification of the DPPC phase diagram as hyaluronan absorbs to the bilayer which results in an Lα-like structure at low temperatures and a decoupling of the leaflets forming an asymmetric bilayer structure.
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| 4. |
- Zander, Thomas, et al.
(författare)
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Influence of the Molecular Weight and the Presence of Calcium Ions on the Molecular Interaction of Hyaluronan and DPPC
- 2020
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Ingår i: Molecules. - : NLM (Medline). - 1431-5157 .- 1420-3049. ; 25:17
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Tidskriftsartikel (refereegranskat)abstract
- Hyaluronan is an essential physiological bio macromolecule with different functions. One prominent area is the synovial fluid which exhibits remarkable lubrication properties. However, the synovial fluid is a multi-component system where different macromolecules interact in a synergetic fashion. Within this study we focus on the interaction of hyaluronan and phospholipids, which are thought to play a key role for lubrication. We investigate how the interactions and the association structures formed by hyaluronan (HA) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) are influenced by the molecular weight of the bio polymer and the ionic composition of the solution. We combine techniques allowing us to investigate the phase behavior of lipids (differential scanning calorimetry, zeta potential and electrophoretic mobility) with structural investigation (dynamic light scattering, small angle scattering) and theoretical simulations (molecular dynamics). The interaction of hyaluronan and phospholipids depends on the molecular weight, where hyaluronan with lower molecular weight has the strongest interaction. Furthermore, the interaction is increased by the presence of calcium ions. Our simulations show that calcium ions are located close to the carboxylate groups of HA and, by this, reduce the number of formed hydrogen bonds between HA and DPPC. The observed change in the DPPC phase behavior can be attributed to a local charge inversion by calcium ions binding to the carboxylate groups as the binding distribution of hyaluronan and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is not changed.
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