6 results on '"Robert M. Ziolek"'
Search Results
2. On the interaction of hyaluronic acid with synovial fluid lipid membranes
- Author
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Elena Gazzarrini, Christian D. Lorenz, Robert M. Ziolek, Dylan M. Owen, and Paul Smith
- Subjects
Molecular Structure ,Hydrogen bond ,Lipid Bilayers ,Phospholipid ,General Physics and Astronomy ,02 engineering and technology ,Molecular Dynamics Simulation ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Molecular dynamics ,Dextran ,Membrane ,chemistry ,Synovial Fluid ,Hyaluronic acid ,Biophysics ,Molecule ,lipids (amino acids, peptides, and proteins) ,Hyaluronic Acid ,Physical and Theoretical Chemistry ,0210 nano-technology ,Lipid bilayer - Abstract
All-atom molecular dynamics simulations have been used to investigate the adsorption of low molecular weight hyaluronic acid to lipid membranes. We have determined the interactions that govern the adsorption of three different molecular weight hyaluronic acid molecules (0.4, 3.8 & 15.2 kDa) to lipid bilayers that are representative of the surface-active phospholipid bilayers found in synovial joints. We have found that both direct hydrogen bonds and water-mediated interactions with the lipid headgroups play a key role in the binding of hyaluronic acid to the lipid bilayer. The water-mediated interactions become increasingly important in stabilising the adsorbed hyaluronic acid molecules as the molecular weight of hyaluronic acid increases. We also observe a redistribution of ions around bound hyaluronic acid molecules and the associated lipid headgroups, and that the degree of redistribution increases with the molecular weight of hyaluronic acid. By comparing this behaviour to that observed in simulations of the charge-neutral polysaccharide dextran (MW ∼ 15 kDa), we show that this charge redistribution leads to an increased alignment of the lipid headgroups with the membrane normal, and therefore to more direct and water-mediated interactions between hyaluronic acid and the lipid membrane. These findings provide a detailed understanding of the general structure of hyaluronic acid–lipid complexes that have recently been presented experimentally, as well as a potential mechanism for their enhanced tribological properties.
- Published
- 2019
3. Morphology of bile salts micelles and mixed micelles with lipolysis products, from scattering techniques and atomistic simulations
- Author
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Yuri Gerelli, Najet Mahmoudi, Rebecca J. L. Welbourn, Maximilian W. A. Skoda, Robert M. Ziolek, Sylvain Prévost, Christian D. Lorenz, Isabelle Grillo, Peter J. Wilde, Margarita Valero, Olivia Pabois, Cécile A. Dreiss, Richard D. Harvey, Myriam M.-L. Grundy, Institut Laue-Langevin (ILL), ILL, King‘s College London, ISIS Neutron and Muon Source (ISIS), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC)-Science and Technology Facilities Council (STFC), Universidad de Salamanca, University of Vienna [Vienna], Physiologie, Environnement et Génétique pour l'Animal et les Systèmes d'Elevage [Rennes] (PEGASE), AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Quadram Institute, Polytechnic University of Marche [Ancona, Italy], European Project: 654000, Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Biotechnology and Biological Sciences Research Council (BBSRC), and Polytechnic University of Marche [Ancona, Italy] / Università Politecnica delle Marche [Ancona, Italia]
- Subjects
Lipolysis products ,medicine.drug_class ,Lipolysis ,02 engineering and technology ,Bile salts ,010402 general chemistry ,01 natural sciences ,Micelle ,Bile Acids and Salts ,Biomaterials ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,X-Ray Diffraction ,Lipid digestion ,Scattering, Small Angle ,medicine ,Moiety ,[CHIM]Chemical Sciences ,Micelles ,Liposome ,Bile acid ,Small-angle X-ray scattering ,Bulk aggregation properties ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical engineering ,Critical micelle concentration ,Liposomes ,Pyrene ,Small-angle scattering ,0210 nano-technology ,[SDV.AEN]Life Sciences [q-bio]/Food and Nutrition - Abstract
Hypotheses\ud \ud Bile salts (BS) are biosurfactants released into the small intestine, which play key and contrasting roles in lipid digestion: they adsorb at interfaces and promote the adsorption of digestive enzymes onto fat droplets, while they also remove lipolysis products from that interface, solubilising them into mixed micelles. Small architectural variations on their chemical structure, specifically their bile acid moiety, are hypothesised to underlie these conflicting functionalities, which should be reflected in different aggregation and solubilisation behaviour.\ud \ud \ud \ud Experiments\ud \ud The micellisation of two BS, sodium taurocholate (NaTC) and sodium taurodeoxycholate (NaTDC), which differ by one hydroxyl group on the bile acid moiety, was assessed by pyrene fluorescence spectroscopy, and the morphology of aggregates formed in the absence and presence of fatty acids (FA) and monoacylglycerols (MAG) – typical lipolysis products – was resolved by small-angle X-ray/neutron scattering (SAXS, SANS) and molecular dynamics simulations. The solubilisation by BS of triacylglycerol-incorporating liposomes – mimicking ingested lipids – was studied by neutron reflectometry and SANS.\ud \ud \ud \ud Findings\ud \ud Our results demonstrate that BS micelles exhibit an ellipsoidal shape. NaTDC displays a lower critical micellar concentration and forms larger and more spherical aggregates than NaTC. Similar observations were made for BS micelles mixed with FA and MAG. Structural studies with liposomes show that the addition of BS induces their solubilisation into mixed micelles, with NaTDC displaying a higher solubilising capacity.
- Published
- 2021
4. On the structure of solid lipid nanoparticles
- Author
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Orathai Loruthai, M. Jayne Lawrence, Demi L. Pink, Robert M. Ziolek, Christian D. Lorenz, Prawarisa Wasutrasawat, and Ann E. Terry
- Subjects
02 engineering and technology ,Crystal structure ,Molecular Dynamics Simulation ,010402 general chemistry ,01 natural sciences ,Biomaterials ,chemistry.chemical_compound ,Molecular dynamics ,Solid lipid nanoparticle ,Molecule ,General Materials Science ,Triglycerides ,Chemistry ,General Chemistry ,021001 nanoscience & nanotechnology ,Small-angle neutron scattering ,Lipids ,0104 chemical sciences ,body regions ,Chemical engineering ,Yield (chemistry) ,Tripalmitin ,Drug delivery ,Nanoparticles ,0210 nano-technology ,Biotechnology - Abstract
Solid lipid nanoparticles (SLNs) have a crystalline lipid core which is stabilised by interfacial surfactants. SLNs are considered favorable candidates for drug delivery vehicles since their ability to store and release organic molecules can be tailored through the identity of the lipids and surfactants used. When stored, polymorphic transitions in the core of drug-loaded SLNs lead to the premature release of drug molecules. Significant experimental studies have been conducted with the aim of investigating the physico-chemical properties of SLNs, however, no molecular scale investigations have been reported on the behaviors that drive SLN formation and their polymorphic transitions. We have therefore used a combination of small angle neutron scattering (SANS) and all-atom molecular dynamics simulations (MS) to yield a detailed atomistic description of the internal structure of an SLN comprising of triglyceride, tripalmitin, and the nonionic surfactant, Brij O10 (C18:1E10). We uncover the molecular scale mechanisms by which the surfactants stabilise the crystalline structure of the SLN lipid core. By comparing these results to simulated liquid and solid aggregates of tripalmitin lipids, we demonstrate how the morphology of the lipids vary between these systems providing further insight into the mechanisms that control drug encapsulation and release from SLNs.
- Published
- 2019
5. Erratum: 'On the solvation of the phosphocholine headgroup in an aqueous propylene glycol solution' [J. Chem. Phys. 148, 135102 (2018)]
- Author
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Christian D. Lorenz, Sylvia E. McLain, M. Jayne Lawrence, Mohamed Ali al-Badri, Richard J. Gillams, Natasha H. Rhys, Robert M. Ziolek, and Louise Collins
- Subjects
chemistry.chemical_compound ,Aqueous solution ,chemistry ,Solvation ,General Physics and Astronomy ,Physical chemistry ,Physical and Theoretical Chemistry ,Polyvinyl alcohol ,Phosphocholine - Published
- 2019
6. On the solvation of the phosphocholine headgroup in an aqueous propylene glycol solution
- Author
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Richard J. Gillams, Mohamed Ali al-Badri, Sylvia E. McLain, Christian D. Lorenz, Robert M. Ziolek, Natasha H. Rhys, Louise Collins, and M. Jayne Lawrence
- Subjects
Phosphorylcholine ,Lipid Bilayers ,General Physics and Astronomy ,Molecular Dynamics Simulation ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Molecular dynamics ,0103 physical sciences ,Physical and Theoretical Chemistry ,Phosphocholine ,Aqueous solution ,010304 chemical physics ,Molecular Structure ,Hydrogen bond ,Bilayer ,Solvation ,Water ,Hydrogen Bonding ,Propylene Glycol ,0104 chemical sciences ,Crystallography ,Membrane ,chemistry ,Phosphatidylcholines ,Solvents ,Solvent effects - Abstract
The atomic-scale structure of the phosphocholine (PC) headgroup in 30 mol. % propylene glycol (PG) in an aqueous solution has been investigated using a combination of neutron diffraction with isotopic substitution experiments and computer simulation techniques - molecular dynamics and empirical potential structure refinement. Here, the hydration of the PC headgroup remains largely intact compared with the hydration of this group in a bilayer and in a bulk water solution, with the PG molecules showing limited interactions with the headgroup. When direct PG interactions with PC do occur, they are most likely to coordinate to the N(CH3)3+ motifs. Further, PG does not affect the bulk water structure and the addition of PC does not perturb the PG-solvent interactions. This suggests that the reason why PG is able to penetrate into membranes easily is that it does not form strong-hydrogen bonding or electrostatic interactions with the headgroup allowing it to easily move across the membrane barrier.
- Published
- 2018
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