| 1. |
- Filippov, Andrei, PhD, 1957-, et al.
(author)
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Diffusion of Ions in Phosphonium Orthoborate Ionic Liquids Studied by 1H and 11B Pulsed Field Gradient NMR
- 2020
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In: Frontiers in Chemistry. - : Frontiers Media S.A.. - 2296-2646. ; 8
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Journal article (peer-reviewed)abstract
- Non-halogenated boron-based ionic liquids (ILs) composed of phosphonium cations and chelated orthoborate anions have high hydrolytic stability, low melting point and exceptional properties for various applications. This study is focused on ILs with the same type of cation, trihexyltetradecylphosphonium ([P6,6,6,14]+), and two orthoborate anions, such as bis(salicylato)borate ([BScB]−) and bis(oxalato)borate ([BOB]−). We compare the results of this study with our previous studies on ILs with bis(mandelato)borate ([BMB]−) and a variety of different cations (tetraalkylphosphonium, dialkylpyrrolidinium and dialkylimidazolium). The ion dynamics and phase behavior of these ILs is studied using 1H and 11B pulsed-field-gradient (PFG) NMR. PFG NMR is demonstrated to be a useful tool to elucidate the dynamics of ions in this class of phosphonium orthoborate ILs. In particular, the applicability of 11B PFG NMR for studying anions without 1H, such as [BOB]−, and the limitations of this technique to measure self-diffusion of ions in ILs are demonstrated and discussed in detail for the first time.
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| 2. |
- Filippov, Andrei, et al.
(author)
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Disordering of phospholipid headgroups induced by a small amount of polyethylene oxide
- 2013
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In: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 51:1, s. 1-3
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Journal article (peer-reviewed)abstract
- We present a 31P NMR spectroscopy study of planar glass-plate-oriented multi-bilayers of dimyristoylphosphatidylcholine (DMPC) with addition of polyethylene oxide (PEO). This work revealed the presence of a new component in the spectra that appeared only with addition of a small fraction of PEO (up to one PEO segment per dimyristoylphosphatidylcholine molecule) and disappeared when larger amounts of PEO were added. We explained this phenomenon as an effect of an inhomogeneous force field induced by the PEO molecules located at a certain depth in the lipid membrane interface region
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| 3. |
- Filippov, Andrei, et al.
(author)
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Effect of curcumin on lateral diffusion in lipid bilayers
- 2016
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In: Mendeleev communications (Print). - : Elsevier BV. - 0959-9436 .- 1364-551X. ; 26:2, s. 109-110
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Journal article (peer-reviewed)abstract
- Lateral diffusion in dimyristoylphosphatidylcholine lipid bilayers decreases in the presence of cholesterol and curcumin, as measured by 1H NMR spectroscopy, but the mechanisms of action of these two compounds are different.
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| 4. |
- Filippov, Andrei, et al.
(author)
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Effect of Curcumin on Lateral Diffusion of Phosphatidylcholines in Saturated and Unsaturated Bilayers
- 2014
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:35, s. 10686-10690
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Journal article (peer-reviewed)abstract
- Curcumin, a dietary polyphenol, is a natural spice with preventive and therapeutic potential for neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Curcumin possesses a spectrum of antioxidant, anti-inflammatory, anticarcinogenic, and antimutagenic properties. Because of this broad spectrum of pharmacological activity, it has been suggested that, like cholesterol, curcumin exerts its effect on a rather basic biological level, such as on lipid bilayers of biomembranes. The effect of curcumin on translational mobility of lipids in biomembranes has not yet been studied. In this work, we used 1H NMR diffusometry to explore lateral diffusion in planar-oriented bilayers of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC) at curcumin concentrations of up to 40 mol % and in the temperature range of 298-333 K. The presence of curcumin at much lower concentrations (∼7 mol %) leads to a decrease in the lateral diffusion coefficient of DOPC by a factor of 1.3 at lower temperatures and by a factor of 1.14 at higher temperatures. For DMPC, the diffusion coefficient decreases by a factor of 1.5 at lower temperatures and by a factor of 1.2 at higher temperatures. Further increasing the curcumin concentration has no effect. Comparison with cholesterol showed that curcumin and cholesterol influence lateral diffusion of lipids differently. The effect of curcumin is determined by its solubility in lipid bilayers, which is as low as 10 mol % that is much less than that of cholesteroĺs 66 mol %.
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| 5. |
- Filippov, Andrei, et al.
(author)
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Phase transition, ordering and lateral diffusion in phospholipid bilayers in the presence of poly(ethylene oxide)
- 2012
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In: Mendeleev communications (Print). - : Elsevier BV. - 0959-9436 .- 1364-551X. ; 22:5, s. 250-251
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Journal article (peer-reviewed)abstract
- The thermal behaviour, molecular orientation and lateral diffusion in the bilayered systems of dimyristoylphosphatidylcholine (DMPC) in the presence of poly(ethylene oxide) (PEO) were studied by NMR and DSC techniques, and it was found that PEO decreases the melting temperature (of vesicles and flat multibilayers) and affects the degree of orientation of DMPC molecules relative to the bilayer normal, but it does not influence the lateral diffusion of DMPC molecules
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| 6. |
- Munavirov, Bulat, et al.
(author)
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Interaction of polyacrylic acid with lipid bilayers : effect of polymer mass
- 2013
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In: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 51:11, s. 750-755
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Journal article (peer-reviewed)abstract
- Polyanion-coated lipid vesicles are proposed to have an appreciable potential for drug delivery because of their ability to control the permeability of lipid bilayers by environmental parameters such as pH and temperature. However, details of the interaction of this class of polymers with lipids and their mechanisms of induced permeability are still being debated. In this work, we applied 1H NOESY to study details of the interaction of polyacrylic acid (PAA) fractions of molecular weights 5 and 240 kDa with dimyristoylphosphatidylcholine vesicles. We showed that PAA of two different molecular masses modifies lipid bilayers increasing disorder and probability of close contact between polar and hydrophobic groups. PAA molecules adsorb near the interface of lipid bilayers but do not penetrate into the hydrophobic core of the bilayer and, thus, cannot participate in formation of transbilayer channels, proposed in earlier works. Increasing the molecular mass of PAA from 5 kDa to 240 kDa does not change the effect of PAA on the bilayer, although PAA240 forms a more compact structure (either intra-molecular or inter-molecular) and interacts more strongly with interface lipid protons
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| 7. |
- Munavirov, Bulat V., et al.
(author)
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Polyacrylic Acid Modifies Local and Lateral Mobilities in Lipid Membranes
- 2014
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In: Journal of Dispersion Science and Technology. - : Informa UK Limited. - 0193-2691 .- 1532-2351. ; 35:6, s. 848-858
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Journal article (peer-reviewed)abstract
- Polyacrylic acid (PAA) is a promising polymer for engineering lipid-based drug-delivery vesicles. Its unique properties allow lowering drug dose and delivery the drug close to the site of its release. To design a successful delivery scheme, however, it is important to understand on the molecular scale how the polymer interacts with lipids under various conditions in the human body. Some aspects of the PAA-lipid interaction can be revealed using physical methods, such as differential scanning microscopy, nuclear magnetic resonance spectroscopy, NMR-diffusometry, and infrared spectroscopy. This work discusses the use of these techniques as well as the peculiarities of preparing vesicular and microscopically aligned PAA-lipid systems.
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| 8. |
- Rohlmann, Patrick, et al.
(author)
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Non-halogenated Ionic Liquid Dramatically Enhances Tribological Performance of Biodegradable Oils
- 2019
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In: Frontiers in Chemistry. - Laussanne : Frontiers Media S.A.. - 2296-2646. ; 7
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Journal article (peer-reviewed)abstract
- It is demonstrated that a phosphonium orthoborate ionic liquid may serve as a wear reducing additive in biodegradable oils at steel-steel surfaces in the boundary lubrication regime. Tribological tests were performed in a ball-on-three plate configuration. A set of surface characterization techniques—SEM/EDS, FIB and white light interferometry were used to characterize surfaces following the tribotests and to observe the formation of any tribofilms. 11B NMR was used to follow changes in the composition of the ionic-liquid-oil blends and to identify boron-containing decomposition products after the tribotests. The ionic liquid reduces the wear of steel surfaces by up to 92% compared to the neat oil at 90°C; it is shown that the reduction in wear can be correlated with the formation of boron enriched patches in the boundary films.
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