Understanding the Effects of Ligand Configuration on Protoporphyrinogen IX Oxidase with Rationally Designed 3-(N-Phenyluracil)but-2-enoates

Protoporphyrinogen IX oxidase (PPO, EC 1.3.3.4) is a promising target for green herbicide discovery. However, the ligand configuration effects on PPO activity were still poorly understood. Herein, we designed 3-(N-phenyluracil)but-2-enoates using our previously developed active fragments exchange and link (AFEL) approach and synthesized a series of novel compounds with nanomolar ranges of Nicotiana tabacum PPO (NtPPO) inhibitory potency and promising herbicidal potency. Our systematic structure-activity relationship investigations showed that the E isomers of 3-(N-phenyluracil)but-2-enoates displayed improved bioactivity than their corresponding Z isomers. Using molecular simulation studies, we found that the E isomers showed a relatively lower entropy change and could sample more stable binding conformation to the receptor than the Z isomers. Our density functional theory (DFT) calculations showed that the E isomers showed higher chemical reactivity and lower electronic chemical potential than their corresponding Z isomers. Compound E-Ic emerged as the optimal compound with a Ki value of 3.0 nM against NtPPO, exhibiting a broader spectrum of weed control than saflufenacil at 37.5-75 g ai/ha and also safe to maize at 75 g ai/ha, which could be considered as a promising lead herbicide for further development.

Cation-Deficient Ce-Substituted Perovskite Oxides with Dual-Redox Active Sites for Thermochemical Applications

Identifying thermodynamically favorable and stable non-stoichiometric metal oxides is of crucial importance for solar thermochemical (STC) fuel production via two-step redox cycles. The performance of a non-stoichiometric metal oxide depends on its thermodynamic properties, oxygen exchange capacity, and its phase stability under high-temperature redox cycling conditions. Perovskite oxides (ABO_3-δ) are being considered as attractive alternatives to the state-of-the-art ceria (CeO_2-δ) due to their high thermodynamic and structural tunability. However, perovskite oxides often exhibit low entropy change compared to ceria, as they generally have one only redox active site, leading to lower mass-specific fuel yields. Herein, we investigate cation-deficient Ce-substituted perovskite oxides as a new class of potential redox materials combining the advantages of perovskites and ceria. We newly synthesized the (Ce_xSr_1-x)_0.95Ti_0.5Mn_0.5O_3-δ (x = 0, 0.10, 0.15, and 0.20; CSTM) series, with dual-redox active sites comprising Ce (at the A-site) and Mn (at the B-site). By introducing a cation deficiency (∼5%), CSTM perovskite oxides with both phase purity (x ≤ 0.15) and high-temperature structural stability under STC redox cycling conditions are obtained. Thermodynamic properties are evaluated by measuring oxygen non-stoichiometry in the temperature range T = 700-1400 °C and the oxygen partial pressure range pO₂ = 1-10^-4 bar. The results demonstrate that CSTM perovskite oxides exhibit a composition-dependent simultaneous increase of enthalpy and entropy change with increasing Ce-substitution. (Ce_0.20Sr_0.80)_0.95Ti_0.5Mn_0.5O_3-δ (CSTM20) showed a combination of large entropy change of ∼141 J (mol-O)^-1 K^-1 and moderate enthalpy change of ∼238 kJ (mol-O)^-1, thereby creating favorable conditions for thermochemical H₂O splitting. Furthermore, the oxidation states and local coordination environment around Mn, Ce, and Ti sites in the pristine and reduced CSTM samples were extensively studied using X-ray absorption spectroscopy. The results confirmed that both Ce (at the A-site) and Mn (at the B-site) centers undergo simultaneous reduction during thermochemical redox cycling.

Dissipation Theory-Based Ecological Protection and Restoration Scheme Construction for Reclamation Projects and Adjacent Marine Ecosystems

According to the 2017 results of the Special Inspector of Sea Reclamation, a substantial number of idle reclamation zones existed in 11 provinces (cities) along the coast of China. To improve the protection level of coastal wetlands and strictly control reclamation activities, it is necessary to carry out ecological restoration of reclamation projects and adjacent marine ecosystems. The characteristics of Guanghai Bay and its reclamation project are typical in China’s coastal areas, making it an optimal representative site for this study. The dissipative structure and entropy theory was used to analyze ecological problems and environmental threats. The analytic hierarchy process was applied to determine the order of the negative entropy flow importance. The entropy increase and decrease mechanism was used to determine an ecological protection and restoration scheme for the reclamation, including the reclamation of wetland resource restoration, shoreline landscape restoration, environmental pollution control, and marine biological resource restoration. Finally, based on system logic, a typical ecological restoration system was constructed east of Guanghai Bay, with the mangrove wetland area as the model in the north and the artificial sandbeach recreation area as the focus in the south.

Investigation of the Pressure Gain Characteristics and Cycle Performance in Gas Turbines Based on Interstage Bleeding Rotating Detonation Combustion

To further improve the cycle performance of gas turbines, a gas turbine cycle model based on interstage bleeding rotating detonation combustion was established using methane as fuel. Combined with a series of two-dimensional numerical simulations of a rotating detonation combustor (RDC) and calculations of cycle parameters, the pressure gain characteristics and cycle performance were investigated at different compressor pressure ratios in the study. The results showed that pressure gain characteristic of interstage bleeding RDC contributed to an obvious performance improvement in the rotating detonation gas turbine cycle compared with the conventional gas turbine cycle. The decrease of compressor pressure ratio had a positive influence on the performance improvement in the rotating detonation gas turbine cycle. With the decrease of compressor pressure ratio, the pressurization ratio of the RDC increased and finally made the power generation and cycle efficiency enhancement rates display uptrends. Under the calculated conditions, the pressurization ratios of RDC were all higher than 1.77, the decreases of turbine inlet total temperature were all more than 19 K, the power generation enhancements were all beyond 400 kW and the cycle efficiency enhancement rates were all greater than 6.72%.

Structural insights into ligand binding features of dual FABP4/5 inhibitors by molecular dynamics simulations

The fatty acid binding protein (FABP) 4 and 5 have been considered as potential targets for the treatment of metabolic diseases. A compensatory upregulation of FABP5 due to the gene ablation of FABP4 in adipocytes indicated the importance of dual FABP4/5 inhibitors. A few compounds have been discovered as dual FABP4/5 inhibitors. However, none exhibited equivalent inhibitory activity against both FABP4 and FABP5, and almost all compounds showed weaker inhibition against FABP5. To provide a better structural understanding for the design of potent dual FABP4/5 inhibitors, molecular dynamics simulations have been performed for 100 ns to disclose the ligand binding features in FABP4 and FABP5 using Amber14, respectively. Key residues were identified by analysis of close contact, hydrogen bond occupancy, binding free energy and alanine scanning mutagenesis. In addition, induced-fit effects have been observed upon ligand binding in the process of simulations. The shifted alkyl chain of ligand in FABP4 was significantly different from that in FABP5 due to the corresponding residues (Phe58^FABP4 and Leu60^FABP5). Thus, to avoid different steric effects made by these two residues, hydrophobic groups of suitable size should be taken into account. Besides, electrostatic and steric effects with Arg107^FABP4 and Arg109^FABP5 should be paid more attention to. The results will facilitate the rational design of dual FABP4/5 inhibitors.

Intramolecular Entropy and Size-Dependent Solution Properties of Nanocrystal-Ligands Complexes

CdSe-stearates nanocrystal-ligands complex as a whole possess strongly temperature- and size-dependent yet well-defined solubility in small organic solvents, which shows little solvent effects as long as the complexes remained intact. A quantitative thermodynamic model is developed to describe such solubility behavior, which differs fundamentally from conventional models for micron colloids. The model reveals that the conformation entropy of the n-alkanoate chain released in dissolution greatly stabilize the colloidal solution but the strong chain-chain interdigitation between adjacent particles in solid diminishes the solubility. These understandings result in "entropic ligands" (see full disclosure in another report (10.1021/acs.nanolett.6b00730)) as the universal means to battle processability challenges of colloidal nanocrystals.

Entropic Ligands for Nanocrystals: From Unexpected Solution Properties to Outstanding Processability

Solution processability of nanocrystals coated with a stable monolayer of organic ligands (nanocrystal-ligands complexes) is the starting point for their applications, which is commonly measured by their solubility in media. A model described in the other report (10.1021/acs.nanolett.6b00737) reveals that instead of offering steric barrier between inorganic cores, it is the rotation/bending entropy of the C-C σ bonds within typical organic ligands that exponentially enhances solubility of the complexes in solution. Dramatic ligand chain-length effects on the solubility of CdSe-n-alkanoates complexes shall further reveal the power of the model. Subsequently, "entropic ligands" are introduced to maximize the intramolecular entropic effects, which increases solubility of various nanocrystals by 10(2)-10(6). Entropic ligands can further offer means to greatly improve performance of nanocrystals-based electronic and optoelectronic devices.