Polyketides have been widely used clinically due to their significant biological activities, but the needed structural and functional diversity cannot be achieved by common chemical synthetic methods. The tool of combinatorial biosynthesis provides the possibility to produce “unnatural” natural drugs, which has achieved initial success. This paper provides an overview for the strategies of combinatorial biosynthesis in producing the structural and functional diversity of polyketides, including the redesign of metabolic flow, polyketide synthase (PKS) engineering, and PKS post-translational modification. Although encouraging progress has been made in the last decade, challenges still exist regarding the rational combinatorial biosynthesis of polyketides. In this review, the perspectives of polyketide combinatorial biosynthesis are also discussed.

Recently, enzymatic peptide synthesis has drawn increasing attention due to its eco-friendly reagents and mild conditions, as compared to traditional chemical peptide synthesis. In this study, we successfully produced an important antioxidant dipeptide precursor, BOC-Tyr-Ala, via a kinetically controlled enzymatic peptide synthesis reaction, catalyzed by the recombinant carboxypeptidase Y (CPY) expressed in P. pastoris GS115. In this reaction, the enzyme activity was 95.043 U/mL, and we used t-butyloxycarbonyl-l-tyrosine-methyl ester (BOC-Tyr-OMe) as the acyl donor and l-alanine (l-Ala) was the amino donor. We optimized the reaction conditions to be: 30 °C, pH 9.5, organic phase (methanol)/aqueous phase = 1:20, BOC-Tyr-OMe 0.05 mol/L, Ala 0.5 mol/L, and a reaction time of 12 h. Under these conditions, the dipeptide yield reached 49.84%. Then, we established the kinetic model of the synthesis reaction in the form of Michaelis–Menten equation according to the concentration–time curve during the process and the transpeptidation mechanism. We calculated the apparent Michaelis constant $K_{\text{m}}^{\text{app}}$ and the apparent maximum reaction rate $r_{\hbox{max} }^{\text{app}}$ to be $2.9946 \times 10^{{^{ - 2} }} {\text{ mol/L}}$ and $2.0406 \times 10^{ - 2} {\text{ mmol/(mL}}\,{\text{h)}}$, respectively.

After the Tianjin Port 8·12 explosion, an enormous amount of potassium dichromate (K₂Cr₂O₇) and butanone (CH₃COCH₂CH₃) leaked into the coastal soil–groundwater system, which potentially threatened the environment and human health. Determining the transport process of hazards is necessary to establish guidelines for remediating the contaminated area. This work aims to investigate the migration of potassium dichromate and butanone in the coastal soil‒groundwater system through a coupling unsaturated–saturated numerical model, incorporating the HYDRUS model into the MODFLOW/MT3D model. In the unsaturated zone, two-dimensional HYDRUS model was applied, and its recharge flux at the bottom boundary was utilized as the input of MODFLOW/MT3D model in the saturated zone. Results showed that Cr₂O₇ ^2- migrated much faster than butanone in the unsaturated zone and reached the water table in about 1 year. In comparison, butanone was unlikely to enter the aquifer even 5 years later with a migration depth of about 2.2 m. Driven by groundwater, the Cr₂O₇ ^2‒ that entered the aquifer migrated about 161 m toward southeast 5 years later. In the saturated zone, the contamination plume covered mainly the southeast area due to the groundwater flow direction.

Crystals of a new organometallic nonlinear optical (NLO) compound, di-μ-chloro-bis[chlorotri(thiourea)bismuth(III)]-pentachloro(thiourea)bismuth-ate(III) (DCBPB), have been successfully grown from formic acid aqueous solutions of thiourea and bismuth chloride by a slow evaporation technique. The crystal structure and atomic composition of DCBPB have been confirmed by single crystal X-ray diffraction (SCXRD), Fourier transform infrared spectra, and elemental analysis. The SCXRD results proved that DCBPB crystallizes in triclinic space group P1 with unit cell dimensions of a = 7.0606(2) Å, b = 8.8106(4) Å, c = 16.3247(8) Å, α = 99.242(4)°, β = 95.309(3)°, γ  = 105.856(3)°, and Z = 2. DCBPB crystal exhibits excellent transmittance from 500 to 2500 nm and green fluorescence with maximum emission at 508 nm. The thermogravimetric-differential scanning calorimetry (TG-DSC) analysis indicates that a solid-phase reaction took place at 170.1 °C, whereas the decomposition temperature of the crystal material was 189 °C. The NLO property obtained by the Kurtz powder test showed that the second harmonic generation efficiency of DCBPB crystal is two-seventh of KDP crystal.

In this study, a new zirconium-mediated cycloaddition for preparing dibenzosilole derivatives was developed using silicon-bridged diynes and electron-withdrawing alkynes as starting materials. The preparation of silicon-bridged diynes from 1-bromide-2-iodobenzene, terminal alkynes, and dimethyldichlorosilane was also studied. Unlike in the previous synthesis methods, much higher yields of electron-withdrawing group-substituted dibenzosilole derivatives were obtained. In addition, a new synthesis strategy for preparing benzonaphthosilole derivatives using internal alkynes, 1,4-dibromobenzene, and electron-withdrawing alkynes as starting materials is proposed. Compared with previous methods, alkyl, phenyl, and electron-withdrawing groups can be successfully introduced onto aromatic rings, and the positions of these substituents can be easily controlled. The cycloaddition reactions for dibenzosilole and benzonaphthosilole derivatives are highly efficient one-pot processes, and the raw materials are available and easily prepared. Using these new methods, a series of novel multi-substituted dibenzonsilole and benzonaphthosilole derivatives were obtained effectively.

A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCo_1−xPt _xO₃/SiO₂ (x = 0.03, 0.05, 0.07, 0.09, and 0.10) were prepared through a simple method of citrate acid complexation combined with impregnation. In a nanocrystallite of LaCo_1−xPt _xO₃, ions of lanthanum, cobalt, and platinum are evenly mixed at the atomic level and confined within the nanocrystallite. In the reduction process, platinum ions were reduced and migrated onto the surface of the nanocrystallite, and the platinum should be highly dispersed owing to the even mixing of the platinum ions in the precursor. When x = 0.05 or lower, the highest dispersion of Pt could be achieved. The highly dispersed Pt is stable, because of the strong interaction between Pt atoms and the support. The catalysts were characterized by BET surface area, temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, CO temperature-programmed desorption, and turnover frequency. Compared with general precious metal Pt catalysts, the LaCo_0.95Pt_0.05O₃/SiO₂ catalyst exhibited better activity for CO oxidation, and it maintained stability at a high temperature of 400 °C for 250 h with complete CO conversion.

Graphene oxide (GO) contains numerous functional groups that facilitate the intercalation of polar solvents. The properties and applications of GO are closely related to its interlayer spacing. We report on the changes in the interlayer spacing of GO after the adsorption of water molecules and the polar organic solvents C₂H₆O₂ (EG), C₃H₇NO (DMF), C₅H₉NO (NMP). Experiments were conducted to investigate the variations in the functional groups and structure of GO after solvent adsorption, and they play a vital role in modeling and verifying the results of molecular dynamics simulation. The most stable GO structures are obtained through molecular dynamics simulation. The expansion of the interlayer spacing of GO after the adsorption of monolayer solvent molecules corresponds to the minimum three-dimensional size of the solvent molecules. The spatial arrangement of solvent molecules also contributes to the changes in interlayer spacing. Most adsorbed molecules are oriented parallel to the carbon plane of GO. However, as additional molecules are adsorbed into the interlaminations of GO, the adsorbed molecules are oriented perpendicular to the carbon plane of GO, and a large space forms between two GO interlayers. In addition, the role of large molecules in increasing interlayer spacing becomes more crucial than that of water molecules in the adsorption of binary solvent systems by GO.

In this study, a new mass model involving superheat, initial temperature, liquid height, evaporator diameter, and flashing time is established to describe the flash evaporation process of water film. Of 469 sets of flash experimental data from three previous researches, 305 sets were applied to optimize parameters, and the other 164 sets were used to verify the practicability of the model. The results showed that the mean relative error between the literature data and the model values was less than 16.3%, and the model statistics proved that the model was well-posed. Then, the kinetic model was obtained using the time derivative of the new mass model. Computational fluid dynamics simulation of water film flash evaporation was studied based on a user-defined function program of the new evaporation kinetic model. The new kinetic model shows more consistency with the experimental phenomena in terms of evaporated mass and temperature compared with the evaporation–condensation model in Fluent software and Gopalakrishna’s model. This new kinetic model can be extended to describe the flash process of water solution under other conditions.

This study investigated the influence of temperature on the performance of forward osmosis (FO) under the condition that the feed solution (FS) temperature was different from draw solution (DS) temperature. An FO model considering the mass and heat transfer between FS and DS was developed, and the FO experiment with ammonium bicarbonate solution as DS and sodium chloride solution as FS was carried out. The predicted water flux and reverse draw solute flux using the developed model coincided with the experimental fluxes. Increases in the temperature of FS or DS yield corresponding increases in the water flux, reverse draw solute flux, and forward rejection of feed solute. Compared with increasing the FS temperature, increasing the DS temperature has a more significant impact on enhancing FO performance. When the temperature of DS increased from 20 to 40 °C, the specific reverse solute flux decreased from 0.231 to 0.190 mol/L.

A thioester-functionalized triphenylamine hole-transporting molecule (TPD-SAc) was synthesized and self-assembled to form a monolayer on an ultra-thin Au film supported on indium-tin oxide glass. The modified surface was characterized by aqueous contact angle, ellipsometer, atomic force microscopy, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectrometer to substantiate the formation of compact and pinhole-free monolayers. The modified organic light emitting diode device [indium-tin oxide/Au (5 nm)/self-assembled monolayers (SAM)/TPD (50 nm)/Alq₃ (40 nm)/TPBI (15 nm)/LiF (1 nm)/Al (100 nm)] showed a luminance of 7303.90 cd/m² and a current efficiency of 8.49 cd/A with 1.78 and 2.29-fold increase, respectively, compared to the control device without SAM. The improvements were attributed to the enhanced compatibility of the organic–inorganic interface, matched energy level by introduction of an energy mediating step and superior hole-injection property of SAM molecules.

To locate and quantify local damage in a simply supported bridge, in this study, we derived a rotational-angle influence line equation of a simply supported beam model with local damage. Using the diagram multiplication method, we introduce an analytical formula for a novel damage-identification indicator, namely the difference of rotational-angle influence lines-curvature (DRAIL-C). If the initial stiffness of the simply supported beam is known, the analytical formula can be effectively used to determine the extent of damage under certain circumstances. We determined the effectiveness and anti-noise performance of this new damage-identification method using numerical examples of a simply supported beam, a simply supported hollow-slab bridge, and a simply supported truss bridge. The results show that the DRAIL-C is directly proportional to the moving concentrated load and inversely proportional to the distance between the bridge support and the concentrated load and the distance between the damaged truss girder and the angle measuring points. The DRAIL-C indicator is more sensitive to the damage in a steel-truss-bridge bottom chord than it is to the other elements.