Reaction Mechanism Generator v3.0: Advances in Automatic Mechanism Generation.

In chemical kinetics research, kinetic models containing hundreds of species and tens of thousands of elementary reactions are commonly used to understand and predict the behavior of reactive chemical systems. Reaction Mechanism Generator (RMG) is a software suite developed to automatically generate such models by incorporating and extrapolating from a database of known thermochemical and kinetic parameters. Here, we present the recent version 3 release of RMG and highlight improvements since the previously published description of RMG v1.0. Most notably, RMG can now generate heterogeneous catalysis models in addition to the previously available gas- and liquid-phase capabilities. For model analysis, new methods for local and global uncertainty analysis have been implemented to supplement first-order sensitivity analysis. The RMG database of thermochemical and kinetic parameters has been significantly expanded to cover more types of chemistry. The present release includes parallelization for faster model generation and a new molecule isomorphism approach to improve computational performance. RMG has also been updated to use Python 3, ensuring compatibility with the latest cheminformatics and machine learning packages. Overall, RMG v3.0 includes many changes which improve the accuracy of the generated chemical mechanisms and allow for exploration of a wider range of chemical systems.

Encapsulation of enzyme via one-step template-free formation of stable organic-inorganic capsules: A simple and efficient method for immobilizing enzyme with high activity and recyclability.

Enzyme encapsulation is a simple, gentle, and general method for immobilizing enzyme, but it often suffers from one or more problems regarding enzyme loading efficiency, enzyme leakage, mechanical stability, and recyclability. Here we report a novel, simple, and efficient method for enzyme encapsulation to overcome these problems by forming stable organic-inorganic hybrid capsules. A new, facile, one-step, and template-free synthesis of organic-inorganic capsules in aqueous phase were developed based on PEI-induced simultaneous interfacial self-assembly of Fmoc-FF and polycondensation of silicate. Addition of an aqueous solution of Fmoc-FF and sodium silicate into an aqueous solution of PEI gave a new class of organic-inorganic hybrid capsules (FPSi) with multi-layered structure in high yield. The capsules are mechanically stable due to the incorporation of inorganic silica. Direct encapsulation of enzyme such as epoxide hydrolase SpEH and BSA along with the formation of the organic-inorganic capsules gave high yield of enzyme-containing capsules (∼1.2 mm in diameter), >90% enzyme loading efficiency, high specific enzyme loading (158 mg protein g(-1) carrier), and low enzyme leakage (<3% after 48 h incubation). FPSi-SpEH capsules catalyzed the hydrolysis of cyclohexene oxide to give (1R, 2R)-cyclohexane-1,2-diol in high yield and concentration, with high specific activity (6.94 U mg(-1) protein) and the same high enantioselectivity as the free enzyme. The immobilized SpEH demonstrated also excellent operational stability and recyclability: retaining 87% productivity after 20 cycles with a total reaction time of 80 h. The new enzyme encapsulation method is efficient, practical, and also better than other reported encapsulation methods.

Nitrosamine formation in amine scrubbing at desorber temperatures.

Amine scrubbing is a thermodynamically efficient and industrially proven method for carbon capture, but amine solvents can nitrosate in the desorber, forming potentially carcinogenic nitrosamines. The kinetics of reactions involving nitrite and monoethanolamine (MEA), diethanolamine (DEA), methylethanolamine (MMEA), and methyldiethanolamine (MDEA) were determined under desorber conditions. The nitrosations of MEA, DEA, and MMEA are first order in nitrite, carbamate species, and hydronium ion. Nitrosation of MDEA, a tertiary amine, is not catalyzed by the addition of CO2 since it cannot form a stable carbamate. Concentrated and CO2 loaded MEA was blended with low concentrations of N-(2-hydroxyethyl) glycine (HeGly), hydroxyethyl-ethylenediamine (HEEDA), and DEA, secondary amines common in MEA degradation. Nitrosamine yield was proportional to the concentration of secondary amine and was a function of CO2 loading and temperature. Blends of tertiary amines with piperazine (PZ) showed n-nitrosopiperazine (MNPZ) yields close to unity, validating the slow nitrosation rates hypothesized for tertiary amines. These results provide a useful tool for estimating nitrosamine accumulation over a range of amine solvents.

Kinetics of N-nitrosopiperazine formation from nitrite and piperazine in CO2 capture.

Piperazine (PZ) is an efficient amine for carbon capture systems, but it can form N-nitrosopiperazine (MNPZ), a carcinogen, from nitrogen oxides (NO(x)) in flue gas from coal or natural gas combustion. The reaction of nitrite with PZ was studied in 0.1 to 5 mol/dm(3) PZ with 0.001 to 0.8 mol CO2/mol PZ at 50 to 135 °C. The reaction forming MNPZ is first order in nitrite, piperazine carbamate species, and hydronium ion. The activation energy is 84 ± 2 kJ/mol with a rate constant of 8.5 × 10(3) ± 1.4 × 10(3) dm(6) mol(-2) s(-1) at 100 °C. The proposed mechanism involves protonation of the carbamate species, nucleophilic attack of the carbamic acid, and formation of bicarbonate and MNPZ. These kinetics and mechanism will be useful in identifying inhibitors and other strategies to reduce nitrosamine accumulation in CO2 capture by scrubbing with PZ or other amines.

Guillain-Barré syndrome complicated by myocarditis.

Guillain-Barré syndrome (GBS) is an autoimmune disease affecting the peripheral nerves, and is frequently associated with triggering events several weeks prior to the onset of symptoms. We report the case of a 68-year-old female who was diagnosed with GBS and subsequently developed myocarditis. She was treated with inotropic support and intravenous immunoglobulin (IVIG), and her condition improved. This presentation of GBS complicated by myocarditis is very rare. We examined the literature regarding this association.