Alkaloids of a new type fromSophora alopecuroides L.

Summary The structures of aloperine and allylaloperine (fromSophora alopecuroides L.) — alkaloids of a new structural type for the genusSophora — have been established by chemical and spectral methods. A number of parameters, NMR spectra, and mass spectra characterizing this class of compounds has been obtained. The partial synthesis of allylaloperine has been performed.All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 30–37, January–February, 1975.     

Interaction between Globular Proteins and Silica Surfaces

The adsorption of bovine serum albumin on silica of three different types, i.e., aerosil, macroporous silica gel, and ground natural quartz, was studied. The IR spectra of this protein adsorbed on aerosil were measured and analyzed. It was shown that the carbonyl groups of albumin macromolecules interact with vicinal hydroxyl groups while imido groups, with individual hydroxyl groups of silica surface. The geminal hydroxyl groups of the surface behaved as single adsorption sites with respect to albumin. The number or such sites on quartz surface was estimated. The IR spectra indicated that the adsorption of albumin macromolecules caused the dehydration of aerosil surface and the appearance of a small amount (to 10%) of unfolded -regions in the secondary structure of the adsorbed protein, while the -helical macromolecular structure remains preserved as a whole. Changes in the tertiary structure of the protein resulted from the adsorption were discussed. Protein macromolecules folded into globules were shown to be tilted with respect to the adsorbent surface.     

Composite materials based on fullerenes C60/C70 and polypropylene prepared via in situ polymerization

New composite materials based on isotactic PP and fullerene were prepared via in situ polymerization with the use of an isospecific metallocene catalytic system. The stress-strain properties, thermophysical characteristics, and reactivities of composites in reactions of high-temperature decomposition, oxidation, and chemiluminescence were studied. The appreciable effect of fullerene on the thermal oxidation and crystallization behavior of composites (an increase in the crystallization temperature by 10 K) was found. It was shown that the protective inhibitory effect of fullerene in PP oxidation reactions is due to the interaction of fullerene nanoparticles with peroxy macroradicals.     

Practical guide for selection of 1H qNMR acquisition and processing parameters confirmed by automated spectra evaluation

In our recent paper, a new technique for automated spectra integration and quality control of the acquired results in qNMR was developed and validated (Monakhova & Diehl, Magn. Res. Chem. 2017, doi: 10.1002/mrc.4591 ). The present study is focused on the influence of acquisition and postacquisition parameters on the developed automated routine in particular, and on the quantitative NMR (qNMR) results in general, which has not been undertaken previously in a systematic and automated manner. Results are presented for a number of model mixtures and authentic pharmaceutical products measured on 500‐ and 600‐MHz NMR spectrometers. The influence of the most important acquisition (spectral width, transmitter [frequency] offset, number of scans, and time domain) and processing (size of real spectrum, deconvolution, Gaussian window multiplication, and line broadening) parameters for qNMR was automatically investigated. Moderate modification of the majority of the investigated parameters from default instrument settings within evaluated ranges does not significantly affect the trueness and precision of the qNMR. Lite Gaussian window multiplication resulted in accuracy improvement of the qNMR output and is recommended for routine measurements. In general, given that the acquisition and processing parameters were selected based on the presented guidelines, automated qNMR analysis can be employed for reproducible high‐precision concentration measurements in practice.     

Investigation into the structural composition of hydroalcoholic solutions as basis for the development of multiple suppression pulse sequences for NMR measurement of alcoholic beverages

An eight‐fold suppression pulse sequence was recently developed to improve sensitivity in ¹H NMR measurements of alcoholic beverages [Magn. Res. Chem. 2011 (49): 734–739]. To ensure that only one combined hydroxyl peak from water and ethanol appears in the spectrum, adjustment to a certain range of ethanol concentrations was required. To explain this observation, the structure of water–ethanol solutions was studied. Hydroalcoholic solutions showed extreme behavior at 25% vol, 46% vol, and 83% vol ethanol according to ¹H NMR experiments. Near‐infrared spectroscopy confirmed the occurrence of four significant compounds (‘individual’ ethanol and water structures as well as two water–ethanol complexes of defined composition – 1 : 1 and 1 : 3). The successful multiple suppression can be achieved for every kind of alcoholic beverage with different alcoholic strengths, when the final ethanol concentration is adjusted to a range between 25% vol and 46% vol (e.g. using dilution or pure ethanol addition). In this optimum region, an individual ethanol peak was not detected, because the ‘individual’ water structure and the 1 : 1 ethanol–water complex predominate. The nature of molecular association in ethanol–water solutions is essential to elucidate NMR method development for measurement of alcoholic beverages. The presented approach can be used to optimize other NMR suppression protocols for binary water–organic solvent mixtures, where hydrogen bonding plays a dominant role. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and Some Biological Properties of Pyrrolo[1,2‐a]indoles

The procedures for the synthesis of substituted pyrrolo[1,2‐a]indoles and some of their biological properties are reviewed.     

Application of modern chemometric methods to the study of equilibria in solutions

The possibility of the spectrometric-chemometric study of equilibria in solutions is demonstrated for substances with strongly overlapping spectra, in particular, using the independent component analysis (MILCA and SIMPLISMA algorithms) and the alternating least squares algorithm (MCR-ALS). Using the chemometric approach allows one to resolve spectral curves, identify species present in the solution, and calculate the characteristics of equilibria. The proposed approach is illustrated on a series of examples (study of a tautomeric equilibrium and complexation reactions).     

Methodology of chemometric modeling of spectrometric signals in the analysis of complex samples

A generalized algorithm of the multivariate simulation of spectrometric data is considered for solving typical analytical problems, like the determination of the concentration of a particular analyte and the assignment of a sample to one of predefined classes. In particular, we considered preliminary data processing, exploratory analysis, optimization of a chemometric model, calculation of performance characteristics, transfer of the model to other spectrometers, and automation of chemometric processing for the routine analysis of samples. To illustrate the potential of the method, we selected a system of bovine and porcine heparin, mixtures of soy and sunflower lecithin, and a set of red and white wine samples as test samples. Partial least squares and discriminant analysis were used as chemometric methods. We used proton nuclear magnetic resonance (1H NMR) to record signals. Using the MATLAB environment, chemometric programs were developed for automated data processing in the context of problems under consideration and for the transfer of multivariate models to other spectrometers. Based on the results obtained, a methodology is proposed for the multivariate analysis of spectrometric data, which can be used in the analysis of various types of matrices and spectrometric signals.     

Chemistry of selenophene

The synthesis of a number of β-diketones and 3, 5-disubstituted pyrazoles with 3-selenienyl radicals has been described.