From amino acid mixtures to peptides in liquid sulphur dioxide on early Earth

The formation of peptide bonds is one of the most important biochemical reaction steps. Without the development of structurally and catalytically active polymers, there would be no life on our planet. However, the formation of large, complex oligomer systems is prevented by the high thermodynamic barrier of peptide condensation in aqueous solution. Liquid sulphur dioxide proves to be a superior alternative for copper-catalyzed peptide condensations. Compared to water, amino acids are activated in sulphur dioxide, leading to the incorporation of all 20 proteinogenic amino acids into proteins. Strikingly, even extremely low initial reactant concentrations of only 50 mM are sufficient for extensive peptide formation, yielding up to 2.9% of dialanine in 7 days. The reactions carried out at room temperature and the successful use of the Hadean mineral covellite (CuS) as a catalyst, suggest a volcanic environment for the formation of the peptide world on early Earth.

Total Synthesis of C-8 Hydroxyl Substituted Lomefloxacin as the Photolysis Impurity

Objective: Photochemical decomposition of lomefloxacin (Lom) is supposed to result in the generation of C-8 substituted impurity and accompanied fluoride. The existence and amount of C-8 hydroxyl substituted Lom could be proposed as the marker to the stability and process consistency. The specific C-8 hydroxyl substituent impurity (1-ethyl-6-fluoro-8-hydroxy-7-(3-methylpiperazin-1-yl )-4-oxo-1,4-dihydroquinoline-3-carboxylic acid) was designed and synthesized to be available. Method: 2,4,5-trifluoro-3-methoxybenzoic acid as the initial reactant was subjected to a series of seven-step reactions, such as acylation, condensation with trans N,N-dimethylamino ethyl acrylate, N-ethylation, cyclization, hydrolysis, condensation with piperazine and acidification. The resultant substance was then purified using HPLC and C18 solid-phase extraction. The structure of C-8 hydroxyl substituted Lom was identified with 1H-NMR, 13C-NMR and HRMS spectroscopes, as well as the purity was determined by HPLC. Conclusion: C-8 hydroxyl substituted Lom was successfully synthesized and purified with purity more than 96%. This photolysis impurity offers an alternative for not only further generic Lom active pharmaceutical ingredient development involved in quality control and consistency evaluation, but also research for the mechanism underlying Lom-induced photosensitivity.

Evaluation of Effectiveness of CO2 Sequestration Using Portland Cement in Geological Reservoir Based on Unified Pipe-network Method

In this paper, we first recapitulate some basic notions of the CO 2 sequestration and numerical model. Next, a mixed model is employed into the CO 2 sequestration framework, for simulating CO 2 geological sequestration processes. The last part of the paper makes extensions to evaluation of the effectiveness of CO 2 sequestration with respect to atmospheric pressure, formation temperature, the initial reactant concentration, fracture aperture, and fracture dip. The results show that reactive Portland cement has a great impact on the effectiveness of CO 2 sequestration, while the proposed mixed model is robust in simulation.

Stochastic Dynamic Model of Sulfate Corrosion Reactions in Concrete Materials considering the Effects of Colored Gaussian Noises

The corrosion reactions in concrete materials subjected to external environment attack can lead to the deterioration of concrete. However, the effects of internal fluctuations on the corrosion reaction process have not been reported in current studies on damage of concrete materials. To comprehensively describe the effects of internal fluctuations, the stochastic dynamic model of corrosion reactions in concrete materials subjected to sulfate attack is established based on the law of mass conservation and random process theory, in which internal fluctuations and the parameters of the chemical system are, respectively, regarded as colored Gaussian noises and a series of random variables. An experiment of sulfate corrosion reactions in concrete material is carried out to verify the effectiveness of the proposed method. Furthermore, the effects of variations of the initial reactant concentrations on the concentration evolution processes of the corrosion products are investigated. Results show that the stochastic dynamical responses of the corrosion reactions in concrete can be comprehensively investigated by the proposed stochastic mathematical model; the probabilistic information of the corrosion products can also be obtained conveniently. The concentration evolution process of sulfate corrosion products is a random process. The experimental data are only some samples of the random process. Concentrations of the corrosion products in concrete materials significantly fluctuate with the variations of the initial reactant concentrations.

Core-Shell Nanocatalysts Obtained in Reverse Micelles: Structural and Kinetic Aspects

Ability to control the metal arrangement in bimetallic nanocatalysts is the key to improving their catalytic activity. To investigate how metal distribution in nanostructures can be modified, we developed a computer simulation model on the synthesis of bimetallic nanoparticles obtained in microemulsions by a one-pot method. The calculations allow predicting the metal arrangement in nanoparticle under different experimental conditions. We present results for two couples of metals, Au/Pt (Δε=0.26 V) and Au/Ag (Δε=0.19 V), but conclusions can be generalized to other bimetallic pairs with similar difference in standard reduction potentials. It was proved that both surface and interior compositions can be controlled at nanometer resolution easily by changing the initial reactant concentration inside micelles. Kinetic analysis demonstrates that the confinement of reactants inside micelles has a strong effect on the reaction rates of the metal precursors. As a result, the final nanocatalyst shows a more mixed core and a better defined shell as concentration is higher.