Effect of a mixture of caffeine and nicotinamide on the solubility of vitamin (B2) in aqueous solution

The effect of caffeine (CAF) and nicotinamide (NMD) on the solubility of a vitamin B2 derivative (FMN) has been evaluated for mixtures containing either a single hydrotrope (CAF or NMD) or the two hydrotropes simultaneously. A model for analysis of ternary systems, which takes into account all possible complexes between the molecules, has been developed and tested with experimental NMR data on the three-component mixture FMN–CAF–NMD. The results indicate that special attention should be given to the concentration of a hydrotropic agent used to enhance the solubility of a particular drug. A decrease in the efficacy of solubility of the vitamin on addition of large amounts of hydrotropic agent is expected in the two-component systems due to the increased proportion of self-association of the hydrotrope. It is found that a mixture of two hydrotropic agents leads to an increase in the solubility of the vitamin in three-component compared to the two-component system. Rather than using just one hydrotropic agent, it is proposed that a strategy for optimising the solubility of aromatic drugs is to use a mixture of hydrotropic agents

Stochastic models (cooperative and non-cooperative) for NMR analysis of the hetero-association of aromatic molecules in aqueous solution

Stochastic cooperative (STOCH-C) and non-cooperative (STOCH-NC) models have been developed for NMR analysis of the hetero-association of aromatic compounds in solution, in order to take into account all physically meaningful association reactions of molecules in which there are no limitations on the lengths of the aggregates and complexes. These algorithmical approaches are compared with previously published basic (BASE) and generalized (GEN) analytical statistical thermodynamical models of hetero-association of biologically active aromatic molecules using the same sets of published NMR data measured under the same solution conditions (0.1 M phosphate buffer, pD = 7.1, T = 298 K). It is shown that, within experimental errors, the BASE analytical model may be used to describe molecular systems characterized by relatively small contributions of hetero-association reactions, whereas the GEN model may be applied to hetero-association reactions of any aromatic compound with different self-association properties. The STOCH-C computational algorithm enabled the effect on hetero-association of the interactions of molecules with different cooperativity parameters of self-association to be estimated for the first time and it is proposed that the algorithm for the stochastic models has great potential for detailed investigation and understanding of the interactions of aromatic molecules in solution

Bi-clustering of metabolic data using matrix factorization tools

Metabolic phenotyping technologies based on Nuclear Magnetic Spectroscopy (NMR) and Mass Spectrometry (MS) generate vast amounts of unrefined data from biological samples. Clustering strategies are frequently employed to provide insight into patterns of relationships between samples and metabolites. Here, we propose the use of a non-negative matrix factorization driven bi-clustering strategy for metabolic phenotyping data in order to discover subsets of interrelated metabolites that exhibit similar behaviour across samples. The proposed strategy incorporates bi-cross validation and statistical segmentation techniques to automatically determine the number and structure of bi-clusters. This alternative approach is in contrast to the widely used conventional clustering approaches that incorporate all molecular peaks for clustering in metabolic studies and require a priori specification of the number of clusters. We perform the comparative analysis of the proposed strategy with other bi-clustering approaches, which were developed in the context of genomics and transcriptomics research. We demonstrate the superior performance of the proposed bi-clustering strategy on both simulated (NMR) and real (MS) bacterial metabolic data

The Difficult Case of Crystallization and Structure Solution for the ParC55 Breakage-Reunion Domain of Topoisomerase IV from Streptococcus pneumoniae

BACKGROUND: Streptococcus pneumoniae is the major cause of community-acquired pneumonia and is also associated with bronchitis, meningitis, otitis and sinusitis. The emergence and increasing prevalence of resistance to penicillin and other antibiotics has led to interest in other anti-pneumonococcal drugs such as quinolones that target the enzymes DNA gyrase and topoisomerase IV. During crystallization and in the avenues to finding a method to determine phases for the structure of the ParC55 breakage-reunion domain of topoisomerase IV from Streptococcus pneumoniae, obstacles were faced at each stage of the process. These problems included: majority of the crystals being twinned, either non-diffracting or exhibiting a high mosaic spread. The crystals, which were grown under conditions that favoured diffraction, were difficult to flash-freeze without loosing diffraction. The initial structure solution by molecular replacement failed and the approach proved to be unviable due to the complexity of the problem. In the end the successful structure solution required an in-depth data analysis and a very detailed molecular replacement search. METHODOLOGY/PRINCIPAL FINDINGS: Crystal anti-twinning agents have been tested and two different methods of flash freezing have been compared. The fragility of the crystals did not allow the usual method of transferring the crystals into the heavy atom solution. Consequently, it was necessary to co-crystallize in the presence of the heavy atom compound. The multiple isomorphous replacement approach was unsuccessful because the 7 cysteine mutants which were engineered could not be successfully derivatized. Ultimately, molecular replacement was used to solve the structure by sorting through a large number of solutions in space group P1 using CNS. CONCLUSIONS/SIGNIFICANCE: The main objective of this paper is to describe the obstacles which were faced and overcome in order to acquire data sets on such difficult crystals and determine phases for successful structure solution

PERMANENT-MAGNET ROTARY MOTORS

Different types of traction motors (DC, asynchronous, valve with excitation from permanent magnets) are compared. It is demonstrated that a valve motor with excitation from permanent magnets is the most suitable for using in electric vehicles and electric buses

The comparative analysis of energetic characteristics of variable-frequency electric drives with direct torque control

The simulation models of variable-frequency electric drives with direct torque control were built in MATLAB / Simulink simulation environment. These models are shown and described in the article. А number of energetic characteristics of the electric drives being investigated are considered. The calculations of these characteristics were made on the computer models and the comparative analysis of the values obtained is given

INVESTIGATIONS OF ELECTRIC POWER QUALITY IN AUTONOMOUS LOW POWER PLANT

Autonomous low power electric power plants working with variable speed energy sources or electric subsystems of cogeneration plants of some type need to increase the low speed or the low voltage of the system. In this paper the investigations and the results of the experiments conducted using different structures are given

POWER UNIT FOR POWER SUPPLY OF AN AUTONOMOUS FACILITY HAVING ABILITY TO CONNECT TO GENERAL INDUSTRIAL POWER SUPPLY IN RECUPERATIVE MICROGENERATION MODE

Fundamental and exploratory research in the field of energetics and rational nature management is currently focused on getting results in the field of the effective development and functioning of energy systems. Such systems are based on modern electrical equipment, including electrical machines and controlled power converters (active rectifiers and regenerative units (AC/DC), direct voltage converters (DC/DC), inverters (DC/AC)), conventional and non-traditional electric power based on renewable energy sources (RES).The Program of basic research in the Russian Federation on a long-term period (2021-2030 years) comprises the actual problems of development of energy supply, energy efficiency, renewable and alternative sources in industry and agriculture, including the issues of production technology, of conversion and storage of electric power.Electric power from the renewable energy sources requires its continuous correction, equalization and buffering i.e. a control system for the system operating modes.The paper presents a project of the power unit that provides both autonomous and traditional operation of a power plant having the possibility of recuperating electrical energy into the network. The structure and the composition of such a power unit is proposed, basic control strategies for an autonomous power generating plant having a capacity of up to 15 kW, operating from the variable low speed engine, also having the other sources of alternative energy with the possibility of power accumulation are considered