| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- Carvalho, José P., et al.
(författare)
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Separation of quadrupolar and paramagnetic shift interactions with TOP-STMAS/MQMAS in solid-state lighting phosphors
- 2020
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 58:11, s. 1055-1070
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Tidskriftsartikel (refereegranskat)abstract
- A new approach for processing satellite-transition magic-angle spinning(STMAS) and multiple-quantum magic-angle spinning (MQMAS) data, basedon the two-dimensional one-pulse (TOP) method, which separates thesecond-rank quadrupolar anisotropy and paramagnetic shift interactions viaa double shearing transformation, is described. This method is particularlyrelevant in paramagnetic systems, where substantial inhomogeneous broadeningmay broaden the lineshapes. Furthermore, it possesses an advantage overthe conventional processing of MQMAS and STMAS spectra because it overcomesthe limitation on the spectral width in the indirect dimension imposedby rotor synchronization of the sampling interval. This method was appliedexperimentally to the 27Al solid-state nuclear magnetic resonance of a seriesof yttrium aluminum garnets (YAGs) doped with different lanthanide ions,from which the quadrupolar parameters of paramagnetically shifted and bulkunshifted sites were extracted. These parameters were then compared withdensity functional theory calculations, which permitted a better understandingof the local structure of Ln substituent ions in the YAG lattice.
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| 6. |
- Knoll, Kevin, et al.
(författare)
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A supramolecular and liquid crystalline water-based alignment medium based on azobenzene-substituted 1,3,5-benzenetricarboxamides
- 2022
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 60:6, s. 563-571
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Tidskriftsartikel (refereegranskat)abstract
- A supramolecular, lyotropic liquid crystalline alignment medium based on an azobenzene-containing 1,3,5-benzenetricarboxamide (BTA) building block is described and investigated. As we demonstrate, this water-based system is suitable for the investigation of various water-soluble analytes and allows for a scaling of alignment strength through variation of temperature. Additionally, alignment is shown to reversibly collapse above a certain temperature, yielding an isotropic solution. This collapse allows for isotropic reference measurements, which are typically needed in addition to those in an anisotropic environment, to be performed using the same sample just by varying the temperature. The medium described thus provides easy access to anisotropic NMR observables and simplifies structure elucidation techniques based thereon.
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| 7. |
- Kuhn, Stefan, et al.
(författare)
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NMReDATA : Tools and applications
- 2021
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 59:8, s. 792-803
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Tidskriftsartikel (refereegranskat)abstract
- The nuclear magn etic resonance extracted data (NMReDATA) format has beenproposed as a way to store, exchange, and disseminate nuclear magneticresonance (NMR) data and physical and chemical metadata of chemical com-pounds. In this paper, we report on analytical workflows that take advantageof the uniform and standardized NMReDATA format. We also give access to arepository of sample data, which can serve for validating software packagesthat encode or decode files in NMReDATA format.
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| 8. |
- Nowacka-Perrin, Agnieszka, et al.
(författare)
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In situ 13C solid-state polarization transfer NMR to follow starch transformations in food
- 2022
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 60:7, s. 671-677
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Tidskriftsartikel (refereegranskat)abstract
- Convenience food products tend to alter their quality and texture while stored. Texture-giving food components are often starch-rich ingredients, such as pasta or rice. Starch transforms depending on time, temperature and water content, which alters the properties of products. Monitoring these transformations, which are associated with a change in mobility of the starch chain segments, could optimize the quality of food products containing multiple ingredients. In order to do so, we applied a simple and efficient in situ 13C solid-state magic angle spinning (MAS) NMR approach, based on two different polarization transfer schemes, cross polarization (CP) and insensitive nuclei enhanced by polarization transfer (INEPT). The efficiency of the CP and INEPT transfer depends strongly on the mobility of chain segments—the time scale of reorientation of the CH-bond and the order parameter. Rigid crystalline or amorphous starch chains give rise to CP peaks, whereas mobile gelatinized starch chains appear as INEPT peaks. Comparing 13C solid-state MAS NMR experiments based on CP and INEPT allows insight into the progress of gelatinization, and other starch transformations, by reporting on both rigid and mobile starch chains simultaneously with atomic resolution by the 13C chemical shift. In conjunction with 1H solid-state MAS NMR, complementary information about other food components present at low concentration, such as lipids and protein, can be obtained. We demonstrate our approach on starch-based products and commercial pasta as a function of temperature and storage.
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| 9. |
- Wieske, Hermina, 1994-, et al.
(författare)
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Non-uniform sampling for NOESY? : A case study on spiramycin
- 2021
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 59:7, s. 723-737
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Tidskriftsartikel (refereegranskat)abstract
- To date, most nuclear magnetic resonance (NMR)-based 3-D structure determinations of both small molecules and of biopolymers utilize the nuclear Overhauser effect (NOE) via NOESY spectra. The acquisition of high-quality NOESY spectra is a prerequisite for quantitative analysis providing accurate interatomic distances. As the acquisition of NOE build-ups is time-consuming, acceleration of the process by the use of non-uniform sampling (NUS) may seem beneficial; however, the quantitativity of NOESY spectra acquired with NUS has not yet been validated. Herein, NOESY spectra with various extents of NUS have been recorded, artificial NUS spectra with two different sampling schemes created, and by using two different NUS reconstruction algorithms the influence of NUS on the data quality was evaluated. Using statistical analyses, NUS is demonstrated to influence the accuracy of quantitative NOE experiments. The NOE-based distances show an increased error as the sampling density decreases. Weak NOE signals are affected more severely by NUS than more intense ones. The application of NUS with NOESY comes at two major costs: the interatomic distances are determined with lower accuracy and long-range correlations are lost.
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| 10. |
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