Stereoelectronic and Dynamical Effects Dictate Nitrogen Inversion during Valence Isomerism in Benzene Imine

Benzene imine (1) ⇌ 1H-azepine (2) isomerization occurs through sequential valence and endo–exo isomerism. Quantum chemical and quasiclassical trajectory (QCT) simulations reveal the coupled reaction pathway ‒ ring-expansion followed by...

Recombinant Production of Arginyl Dipeptides by l-Amino Acid Ligase RizA Coupled with ATP Regeneration

Arginyl dipeptides like Arg-Ser, Arg-Ala, and Arg-Gly are salt-taste enhancers and can potentially be used to reduce the salt content of food. The l-amino acid ligase RizA from B. subtilis selectively synthesizes arginyl dipeptides. However, industrial application is prevented by the high cost of the cofactor adenosine triphosphate (ATP). Thus, a coupled reaction system was created consisting of RizA and acetate kinase (AckA) from E. coli providing ATP regeneration from acetyl phosphate. Both enzymes were recombinantly produced in E. coli and purified by affinity chromatography. Biocatalytic reactions were varied and analyzed by RP-HPLC with fluorescence detection. Under optimal conditions the system produced up to 5.9 g/L Arg-Ser corresponding to an ATP efficiency of 23 g Arg-Ser per gram ATP. Using similar conditions with alanine or glycine as second amino acid, 2.6 g/L Arg-Ala or 2.4 g/L Arg Gly were produced. The RizA/AckA system selectively produced substantial amounts of arginyl dipeptides while minimizing the usage of the expensive ATP.

Blow-up Properties of a Coupled System of Reaction-Diffusion Equations

This paper is concerned with a Coupled Reaction-diffusion system defined in a ball with homogeneous Dirichlet boundary conditions. Firstly, we studied the blow-up set showing that, under some conditions, the blow-up in this problem occurs only at a single point. Secondly, under some restricted assumptions on the reaction terms, we established the upper (lower) blow-up rate estimates. Finally, we considered the Ignition system in general dimensional space as an application to our results.

Design and Analysis of Mathematical Model for the Concentration of Pollution and River Water Quality

This paper mainly focuses on the recent advances in the mathematical models that provide the ability to predict the contaminant concentration levels of river water. The study represents an attempt for the researchers to study the problem of pollution, and we think that these mathematical analyses would provide better planning for water quality control. The model consists of a pair of coupled reaction Advection-diffusion equations for the pollutant and dissolved oxygen concentrations. Numerical solutions are obtained and some important inferences are drawn through simulation study. The Advection-Diffusion equation is characterized by the reaction term whenever it depends on concentration of the contaminants and in this case the original single Advection-diffusion equation will evolve to be a system of equations. It is no ticked that the higher are diffusion and reaeration coefficients, the faster is the river purity.

Coupled reaction channels study of the ¹⁶O(d,⁶Li) reaction

The transfer 16O(d,6Li)12C reaction has been studied within the coupled reaction channels (CRC) approach, inluding both the direct and indirect α transfer processes. The obtained results show an important contribution of the indirect α transfer via the 2+ and 4+ states of 12C. The CRC results show that the best-fit α spectroscopic factors of 16O becomes smaller when the indirect transfer processes are taken into account. The α spectroscopic factors deduced from the present CRC analysis of the 16O(d,6Li)12C reaction data measured at Ed=54.25 and 80 MeV are quite close to each other.