Emergence of Inequality in Income and Wealth Dynamics.

Increasing wealth inequality is a significant global issue that demands attention. While the distribution of wealth varies across countries based on their economic stages, there is a universal trend observed in the distribution function. Typically, regions with lower wealth values exhibit an exponential distribution, while regions with higher wealth values demonstrate a power-law distribution. In this review, we introduce measures that effectively capture wealth inequality and examine wealth distribution functions within the wealth exchange model. Drawing inspiration from the field of econophysics, wealth exchange resulting from economic activities is likened to a kinetic model, where molecules collide and exchange energy. Within this framework, two agents exchange a specific amount of wealth. As we delve into the analysis, we investigate the impact of various factors such as tax collection, debt allowance, and savings on the wealth distribution function when wealth is exchanged. These factors play a crucial role in shaping the dynamics of wealth distribution.

Avalanche size distribution of an integrate-and-fire neural model on complex networks.

We considered the neural avalanche dynamics of a modified integrate-and-fire model on complex networks, as well as the neural dynamics in a fully connected network, random network, small-world network, and scale-free network. We observed the self-organized criticality of the neural model on complex networks. The probability distribution of the avalanche size and lifetime follow the power law at the critical synaptic strength. Neuronal dynamics on a complex network are not universal. The critical exponents of the avalanche dynamics depend on the structure of the complex network. We observed that the critical exponents deviate from the mean-field value.

Electrochemical synthesis of formic acid from CO2 catalyzed by Shewanella oneidensis MR-1 whole-cell biocatalyst.

The electro-biocatalytic conversion of CO2 into formic acid using whole-cell and isolated biocatalysts is useful as an alternative route for CO2 sequestration. In this study, Shewanella oneidensis MR-1 (S. oneidensis MR-1), a facultative aerobic bacterium that has been extensively studied for its utility as biofuel cells as well as for the detoxification of heavy metal oxides (i.e., MnO2, uranium), has been applied for the first time as a whole-cell biocatalyst for formic acid synthesis from gaseous CO2 and electrons supplied from an electrode. S. oneidensis MR-1, when aerobically grown in Luria-Bertani (LB) medium, exhibited its ability as a whole-cell biocatalyst for the conversion of CO2 into formic acid with moderate productivity of 0.59 mM h-1 for 24 h. In addition, an optimization of growth conditions of S. oneidensis MR-1 resulted in a remarkable increase in productivity. The CO2 reduction reaction catalyzed by S. oneidensis MR-1, when anaerobically grown in newly optimized LB medium supplemented with fumarate and nitrate, exhibited 3.2-fold higher productivity (1.9 mM h-1 for 72 h) compared to that grown aerobically in only LB medium. Furthermore, the average conversion rate of formic acid synthesis catalyzed by S. oneidensis MR-1 when grown in the optimal medium over a period of 72 h was 3.8 mM h-1 g-1 wet-cell, which is 9.6-fold higher than that catalyzed by Methylobacterium extorquens AM1 whole-cells in our previous study.

Rational design of paraoxonase 1 (PON1) for the efficient hydrolysis of organophosphates.

A rational design of paraoxonase 1 based on molecular docking discovered H115W/T332S and I74F/H115W/T332S mutants exhibited a 40-fold increase in catalytic efficiency (kcat/Km) toward the hydrolysis of two toxic and popular organophosphates (diethyl-paraoxon and dimethyl-paraoxon). Moreover, the conversion of the paraoxons (741.3-825.6 mg L(-1)) by the evolved mutants was 42-60-fold faster than that by the wild type.

Insights into the Lactonase Mechanism of Serum Paraoxonase 1 (PON1): Experimental and Quantum Mechanics/Molecular Mechanics (QM/MM) Studies.

Serum paraoxonase 1 (PON1) is a versatile enzyme for the hydrolysis of various substrates (e.g., lactones, phosphotriesters) and for the formation of a promising chemical platform γ-valerolactone. Elucidation of the PON1-catalyzed lactonase reaction mechanism is very important for understanding the enzyme function and for engineering this enzyme for specific applications. Kinetic study and hybrid quantum mechanics/molecular mechanics (QM/MM) method were used to investigate the PON1-catalyzed lactonase reaction of γ-butyrolactone (GBL) and (R)-γ-valerolactone (GVL). The activation energies obtained from the QM/MM calculations were in good agreement with the experiments. Interestingly, the QM/MM energy barriers at MP2/3-21G(d,p) level for the lactonase of GVL and GBL were respectively 14.3-16.2 and 11.5-13.1 kcal/mol, consistent with the experimental values (15.57 and 14.73 kcal/mol derived from respective kcat values of 36.62 and 147.21 s(-1)). The QM/MM energy barriers at MP2/6-31G(d) and MP2/6-31G(d,p) levels were also in relatively good agreements with the experiments. Importantly, the difference in the QM/MM energy barriers at MP2 level with all investigated basis sets for the lactonase of GVL and GBL were in excellent agreement with the experiments (0.9-3.1 and 0.8 kcal/mol, respectively). A detailed mechanism for the PON1-catalyzed lactonase reaction was also proposed in this study.

Development of thermostable Candida antarctica lipase B through novel in silico design of disulfide bridge.

Lipase B from Candida antarctica (CalB) is a versatile biocatalyst for various bioconversions. In this study, the thermostability of CalB was improved through the introduction of a new disulfide bridge. Analysis of the B-factors of residue pairs in CalB wild type (CalB-WT) followed by simple flexibility analysis of residues in CalB-WT and its designated mutants using FIRST server were newly proposed to enhance the selective power of two computational tools (MODIP and DbD v1.20) to predict the possible disulfide bonds in proteins for the enhancement of thermostability. Five residue pairs (A162-K308, N169-F304, Q156(-) L163, S50-A273, and S239C-D252C) were chosen and the respective amino acid residues were mutated to cysteine. In the results, CalB A162C-K308C showed greatly improved thermostability while maintaining its catalytic efficiency compared to that of CalB-WT. Remarkably, the temperature at which 50% of its activity remained after 60-min incubation (T6°50) of CalB A162C_K308C was increased by 8.5°C compared to that of CalB-WT (55 and 46.5°C, respectively). Additionally, the half-life at 50°C of CalB A162C-K308C was 4.5-fold higher than that of CalB-WT (220 and 49 min, respectively). The improvement of thermostability of CalB A162C-K308C was elucidated at the molecular level by molecular dynamics (MD) simulation.