Molecular interaction and partitioning in α-keratin using 1 H NMR spin-lattice ( T 1 ) relaxation times

The interactions between small molecules and keratins are poorly understood. In this paper, a nuclear magnetic resonance method is presented to measure changes in the 1 H T 1 relaxation times of small molecules in human hair keratin to quantify their interaction with the fibre. Two populations of small-molecule compounds were identified with distinct relaxation times, demonstrating the partitioning of the compounds into different keratin environments. The changes in relaxation time for solvent in hair compared with bulk solvent were shown to be related to the molecular weight (MW) and the partition coefficient, LogP, of the solvent investigated. Compounds with low MWs and high hydrophilicities had greater reductions in their T 1 relaxation times and therefore experienced increased interactions with the hair fibre. The relative population sizes were also calculated. This is a significant step towards modelling the behaviour of small molecules in keratinous materials and other large insoluble fibrous proteins.

Quantitative proton nuclear magnetic resonance method for simultaneous analysis of fluticasone propionate and azelastine hydrochloride in nasal spray formulation

A facile, rapid, accurate and selective quantitative proton nuclear magnetic resonance ( 1 H-qNMR) method was developed for the simultaneous determination of fluticasone propionate (FLP) and azelastine hydrochloride (AZH) in pharmaceutical nasal spray for the first time. The 1 H-qNMR analysis of the studied analytes was performed using inositol as the internal standard and dimethyl sulfoxide- d 6 (DMSO- d 6 ) as the solvent. The quantitative selective proton signal of FLP was doublet of doublet at 6.290, 6.294, 6.316 and 6.319 ppm, while that of AZH was doublet at 8.292 and 8.310 ppm. The internal standard (inositol) produced a doublet signal at 3.70 and 3.71 ppm. The method was rectilinear over the concentration ranges of 0.25–20.0 and 0.2–15.0 mg ml −1 for FLP and AZH, respectively. No labelling or pretreatment steps were required for NMR analysis of the studied analytes. The proposed 1 H-qNMR method was validated efficiently according to the International Council on Harmonisation guidelines in terms of linearity, limit of detection, limit of quantification, accuracy, precision, specificity and stability. Moreover, the method was applied to assay the analytes in their combined nasal spray formulation. The results ensured the linearity ( r 2 > 0.999), precision (% RSD < 1.5), stability, specificity and selectivity of the developed method.

Quantitative 1H Nuclear Magnetic Resonance Method for Assessing the Purity of Dipotassium Glycyrrhizinate

A simple, rapid, accurate, and selective quantitative method based on 1H nuclear magnetic resonance (qNMR) was successfully established and developed for assessing the purity of dipotassium glycyrrhizinate (KG). In this study, using potassium hydrogen phthalate and fumaric acid as internal standard (IS), several important experimental parameters, such as relaxation delay and pulse angle, were explored. Reliability, specificity, linearity, limit of quantification, precision, stability, and accuracy were also validated. Calibration results obtained from qNMR were consistent with those obtained from HPLC coupled with ultraviolet detection. The proposed method, independent of the reference standard substance, is a useful, reliable, and practical protocol for the determination of KG and glycyrrhizin analogs.

INFLUENCE OF THE COMPOSITION FATTY ACIDS OF PHOSPHOLIPID CONTAINED IN SUNFLOWER LECITHINS ON THE PROCESS OF MICELLE FORMATION IN NONPOLAR SOLVENTS

Проведен сравнительный анализ особенностей химического состава лецитинов, полученных из подсолнечных масел олеинового и линолевого типов, и процесса мицеллообразования молекул фосфолипидов указанных лецитинов в неполярных растворителях. Определено, что содержание насыщенных жирных кислот в фосфолипидах подсолнечного лецитина линолевого типа в 2 раза выше, чем в фосфолипидах олеинового типа, а содержание полиненасыщенных жирных кислот, превалирующей из которых является линолевая – 63,36 против 15,54%, в 4 раза. Содержание мононенасыщенных жирных кислот, главным образом олеиновой, в фосфолипидах подсолнечного лецитина олеинового типа в 5 раз выше по сравнению с фосфолипидами линолевого типа, 72,63 и 14,32% соответственно. Далее исследовали процесс мицеллообразования фосфолипидов подсолнечных лецитинов олеинового типа. Установлено, что значения критической концентрации мицеллообразования ККМ1 растворов фосфолипидов подсолнечных лецитинов олеинового типа в модельном масле и CCl4 ниже аналогичных значений растворов фосфолипидов лецитинов линолевого типа: 0,041 против 0,052 и 0,078 против 0,098 соответственно при температуре t 20°С; 0,052/0,061 и 0,113/0,117 соответственно при t 35°С; 0,071/0,083 и 0,142/0,149 соответственно при t 45°С. Показано, что способность к мицеллообразованию фосфолипидов подсолнечных лецитинов олеинового типа в CCl4 ниже, чем в модельном масле. Подтверждена целесообразность и эффективность использования CCl4 в целях снижения степени мицеллообразования фосфолипидов подсолнечных лецитинов олеинового типа при проведении пробоподготовки для разработки способа определения кислотного числа указанных лецитинов с применением импульсного метода ядерного магнитного резонанса. A comparative analysis of the chemical composition of lecithins obtained from sunflower oils of the oleic and linoleic types and the process of micelle formation of phospholipid molecules of these lecithins in nonpolar solvents is carried out. It was determined that the content of saturated fatty acids in phospholipids of sunflower lecithin of the linoleic type is 2 times higher than in oleic type phospholipids, and the content of polyunsaturated fatty acids, the predominant of which is linoleic – 63,36 vs 15,54%, is 4 times higher. The content of monounsaturated fatty acids, mainly oleic, in phospholipids of sunflower lecithin of the oleic type is 5 times higher compared to linoleic type phospholipids, 72,63 and 14,32%, respectively. Next, the process of micelle formation of phospholipids of sunflower lecithins of the oleic type was studied. It is established that the critical concentration of micelle formation ККМ1 solutions of phospholipid oleic sunflower lecithins type in the model oil and CCl4 lower values of solutions of phospholipids lecithins linoleic type: 0,041 vs 0,052 and 0,078 vs 0,098 respectively at a temperature of 20°C; 0,052/0,061 and 0,113/0,117 respectively at t 35°C; 0,071/0,083 and 0,142/0,149 respectively at t 45°C. It is shown that the ability to micelle formation of phospholipids of sunflower lecithins of the oleic type in CCl4 is lower than in the model oil. The expediency and efficiency of using CCl4 in order to reduce the degree of micelle formation of sunflower lecithin phospholipids of the oleic type during sample preparation for the development of a method for determining the acid number of these lecithins using the pulsed nuclear magnetic resonance method was confirmed.

STUDY OF COMPOSITION OF HIGH-VISCOUS HEAVY OILS BY METHOD OF NUCLEAR MAGNETIC RESONANT SPECTROSCOPY

The work uses the nuclear magnetic resonance method to study the composition of heavy high-viscosity oils of various fields of the Volga Ural oil and gas basin. The spectra were recorded on a Bruker Avance III 500MHz high resolution NMR spectrometer with operating frequencies of 1H (500.1 MHz) and 13C (125.8 MHz) at a constant sample temperature in CDCl3. It is established that the oil of the studied field in its physical and chemical characteristics, structural group composition of resins, asphaltenes and oil components is a typical representative of aromatic oils. Oil samples are characterized by high density, a high content of tar-asphaltene compounds and sulfur. In the 1H NMR scale, methylene and methine signals appear in the range from 1.0 to 2.3 ppm: β-CH2, some β-CH groups in aromatic compounds and β-CH, CH2-groups in hydroaromatic compounds, and in the 13C NMR scale they are in the range from 22 to 60 ppm: methylene group (CH2-) in naphthenic fragments, etc. An analysis of the aromaticity coefficients obtained from the 1H and 13C NMR spectra shows a high convergence of the results and indicates a high degree of aromatic condensation in oil samples with a density of 950 kg/m3, a viscosity of 7200 mPa*s at 20 °C and a density of 948 kg/m3, viscosity 1000 mPa·s (FHA=0.046-0.081). With an increase in viscosity, there is a clear tendency to increase the aromaticity coefficient and the average chain length. It follows from the results of the 1H NMR spectra of oils with different origins, viscosities and processing that crude and refined oils may differ in water and olefin signals, and from 13C NMR analysis for oils the most important results were obtained when assessing the concentration of primary, tertiary and aromatic carbon.

Local Structures of Two-Dimensional Zeolites—Mordenite and ZSM-5—Probed by Multinuclear NMR

Mesostructured pillared zeolite materials in the form of lamellar phases with a crystal structure of mordenite (MOR) and ZSM-5 (MFI) were grown using CTAB as an agent that creates mesopores, in a one-pot synthesis; then into the CTAB layers separating the 2D zeolite plates were introduced by diffusion the TEOS molecules which were further hydrolyzed, and finally the material was annealed to remove the organic phase, leaving the 2D zeolite plates separated by pillars of silicon dioxide. To monitor the successive structural changes and the state of the atoms of the zeolite framework and organic compounds at all the steps of the synthesis of pillared MOR and MFI zeolites, the nuclear magnetic resonance method (NMR) with magic angle spinning (MAS) was applied. The 27Al and 29Si MAS NMR spectra confirm the regularity of the zeolite frameworks of the as synthetized materials. Analysis of the 1H and 13C MAS NMR spectra and an experiment with variable contact time evidence a strong interaction between the charged “heads” –[N(CH3)3]+ of CTAB and the zeolite framework at the place of [AlO4]− location. According to 27Al and 29Si MAS NMR the evacuation of organic cations leads to a partial but not critical collapse of the local zeolite structure.