| 1. |
- Altaib, Mohamed S., et al.
(författare)
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Synthesis and NMR elucidation of novel pentacycloundecane-based peptides
- 2010
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 48:6, s. 435-442
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and NMR elucidation of two novel pentacycloundecane (PCU)-based peptides are reported. The PCU cage amino acids were synthesised as racemates and the incorporation of the cage amino acid with (S)-natural amino acids produced diastereomeric peptides. The diastereomeric 'cage' peptides were separated using preparative HPLC and the NMR elucidation of these PCU containing peptides are reported for the first time. The H-1 and C-13 NMR spectra showed series of overlapping signals of the cage skeleton and that of the peptide, making it extremely difficult to resolve the structure using one-dimensional NMR techniques only. The use of two-dimensional NMR techniques proved to be a highly effective tool in overcoming this problem.
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| 2. |
- Antzutkin, Oleg
(författare)
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Amyloidosis of Alzheimer's A peptides : solid-state nuclear magnetic resonance, electron paramagnetic resonance, transmission electron microscopy, scanning transmission electron microscopy and atomic force microscopy studies
- 2004
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 42:2, s. 231-246
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation cascade for Alzheimer's amyloid-β peptides, its relevance to neurotoxicity in the course of Alzheimer's disease and experimental methods useful for these studies are discussed. Details of the solid-phase peptide synthesis and sample preparation procedures for Alzheimer's β-amyloid fibrils are given. Recent progress in obtaining structural constraints on Aβ-fibrils from solid-state NMR and scanning transmission electron microscopy (STEM) data is discussed. Polymorphism of amyloid fibrils and oligomers of the 'Arctic' mutant of Aβ(1-40) was studied by 1H,13C solid-state NMR, transmission electron microscopy (TEM) and atomic force microscopy (AFM), and a real-time aggregation of different polymorphs of the peptide was observed with the aid of in situ AFM. Recent results on binding of Cu(II) ions and Al-citrate and Al-ATP complexes to amyloid fibrils, as studied by electron paramagnetic resonance (EPR) and solid-state 27Al NMR techniques, are also presented.
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| 3. |
- Arkhipov, Victor, et al.
(författare)
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Micelle structure and molecular self-diffusion in isononylphenol ethoxylate–water systems
- 2013
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 51:7, s. 424-430
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Tidskriftsartikel (refereegranskat)abstract
- The structure and dynamic properties of micellar solutions of nonionic surfactants of a series of isononylphenol ethoxylates, C9H19C6H4O(C2H4O)nH (where n = 6,8,9,10, and 12), were studied by NMR diffusometry, dynamic light scattering, and viscosimetry. The sizes of the micelles were determined for different surfactants and at different surfactant concentrations. The numbers of water molecules bound by a micelle and by one oxyethylene group of the surfactant were estimated
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| 4. |
- Arkhipov, Victor P., et al.
(författare)
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Dynamic and molecular association in premicellar aqueous solutions of dicarboxylate amino acid-based surfactant as studied by 1H NMR
- 2022
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 60:3, s. 359-368
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Tidskriftsartikel (refereegranskat)abstract
- We examined a series of amino acid-based surfactants with two carboxylic groups separated by a spacer of one, two, or three carbon atoms with sodium and calcium counterions in the premicellar concentration region near the CMC. 1H NMR spectroscopy and NMR diffusometry techniques were used to study the local environment, association and translational dynamics of the surfactant’s molecules. We measured the self-diffusion coefficients of the micelles, calculated the effective hydrodynamic radii, and determined the temperature region in which the premicelles exist. With an increase in temperature from 295 to 335 K, the premicellar state of the surfactant is replaced by the monomeric state.
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| 5. |
- Arkhipov, Victor P., et al.
(författare)
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Micellar and solubilizing properties of rhamnolipids
- 2023
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 61:6, s. 345-355
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Tidskriftsartikel (refereegranskat)abstract
- We studied the micellar and solubilizing properties of aqueous solutions of unfractionated rhamnolipids produced by Pseudomonas aeruginosa. We used nuclear magnetic resonance (NMR) diffusometry, dynamic light scattering, and conductometry to measure the critical micelle concentration (CMC) of rhamnolipid solutions and determined the effective hydrodynamic radii of rhamnolipid monomers and micelles. Based on selective measurements of the self-diffusion coefficients of molecules, performed by NMR diffusometry, the solubilizing properties of rhamnolipids were studied depending on their concentration in solution; aromatic hydrocarbons, benzene, toluene, ethylbenzene, and para-xylene were taken as solubilizates. On the basis of the measurement results, we estimated the distribution coefficient of the solubilizate between the micellar (solubilized) and free (in the aqueous phase) states and the solubilizing capacity of rhamnolipid micelles.
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| 6. |
- Arkhipov, Victor P., et al.
(författare)
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Study of the premicellar state in aqueous solutions of sodium dodecyl sulfate by nuclear magnetic resonance diffusion
- 2021
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 59:11, s. 1126-1133
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Tidskriftsartikel (refereegranskat)abstract
- Self‐diffusion coefficients of sodium dodecyl sulfate (SDS) were measured in aqueous solutions in the premicellar range of the SDS concentrations 7‐34.7 mM and temperatures 30‐900C. Average effective hydrodynamic radii and aggregation numbers of SDS in the premicellar region were determined. At C < CMC at all temperatures, the SDS solution is the solution of monomers. At C > CMC the increase of temperature leads to decrease in the effective hydrodynamic radii and the average aggregation numbers. At C >> CMC, it is impossible to reach the monomeric state by increasing the temperature.
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| 7. |
- Arkhipov, Victor P., et al.
(författare)
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The efficiency of micellar solubilization of naphthalene from aqueous solutions using rhamnolipid as a biological surfactant according to NMR diffusometry
- 2024
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X.
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.The micellar solubilization of naphthalene from its saturated aqueous solutions using the biosurfactant rhamnolipid was studied. Using the NMR diffusion method, selective measurements of the self-diffusion coefficients of molecules of all components of the solution—naphthalene, rhamnolipid, and water—were carried out at various rhamnolipid concentrations from 0.06 to 100 g/L. Based on the results of diffusometry, the distribution of naphthalene molecules between the states free in solution and states bound by micelles was found. With an increase in the concentration of rhamnolipids, the proportion of bound naphthalene molecules increases from 50% at CRL = 2 g/L to 100% at CRL ≥ 50 g/L. The micelle-water partition coefficient Km and the molar solubilization ratio MSR were calculated.
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| 8. |
- Aski, Sahar Nikkhou, et al.
(författare)
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Inclusion complexes of cryptophane–E with dichloromethane and chloroform : A thermodynamic and kinetic study using the 1D-EXSY NMR method
- 2008
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 46:12, s. 1135-1140
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Tidskriftsartikel (refereegranskat)abstract
- Complexation equilibria and kinetics of exchange of chloroform and dichloromethane molecules between the cavity of cryptophane-E and bulk solution were investigated using NMR methods. Using one dimensional magnetization transfer (1D-EXSY type sequence), chemical exchange rates were measured in different temperature ranges, limited by the equilibrium constant values of the complexes and the boiling points of the guest substances. From the kinetic data, activation energies were calculated using the Arrhenius equation. From the temperature dependence of the association constant data, the enthalpy and entropy of complexation were estimated and compared with values for similar complexes of other cryptophanes.
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| 9. |
- Banyai, Istvan, et al.
(författare)
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Simple O-17 NMR method for studying electron self-exchange reaction between UO22+ and U4+ aqua ions in acidic solution
- 2016
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Ingår i: Magnetic Resonance in Chemistry. - : WILEY-BLACKWELL. - 0749-1581 .- 1097-458X. ; 54:6, s. 444-450
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Tidskriftsartikel (refereegranskat)abstract
- O-17 NMR spectroscopy is proven to be suitable and convenient method for studying the electron exchange by following the decrease of O-17-enrichment in (UOO2+)-O-17 ion in the presence of U4+ ion in aqueous solution. The reactions have been performed at room temperature using I=5MClO(4)(-) ionic medium in acidic solutions in order to determine the kinetics of electron exchange between the U4+ and UO22+ aqua ions. The rate equation is given as R = a[H+](-2) + R, where R is an acid independent parallel path. R depends on the concentration of the uranium species according to the following empirical rate equation: R = k(1)[UO2+](1/2)[U4+](1/2) + k(2)[UO2+](3/2)[U4+](1/2). The mechanism of the inverse H+ concentration-dependent path is interpreted as equilibrium formation of reactive UO2+ species from UO22+ and U4+ aqua ions and its electron exchange with UO22+. The determined rate constant of this reaction path is in agreement with the rate constant of UO22+-UO2+, one electron exchange step calculated by Marcus theory, match the range given experimentally of it in an early study. Our value lies in the same order of magnitude as the recently calculated ones by quantum chemical methods. The acid independent part is attributed to the formation of less hydrolyzed U(V) species, i.e. UO3+, which loses enrichment mainly by electron exchange with UO22+ ions. One can also conclude that O-17 NMR spectroscopy, or in general NMR spectroscopy with careful kinetic analysis, is a powerful tool for studying isotope exchange reactions without the use of sophisticated separation processes. Copyright (C) 2015 John Wiley amp; Sons, Ltd.
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| 10. |
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