A magnetic biocatalyst based on mussel-inspired polydopamine and its acylation of dihydromyricetin

A support made of mussel-inspired polydopamine-coated magnetic iron oxide nanoparticles (PD-MNPs) was prepared and characterized. The widely used Aspergillus niger lipase (ANL) was immobilized on the PD-MNPs (ANL@PD-MNPs) with a protein loading of 138 mg/g and an activity recovery of 83.6% under optimized conditions. For the immobilization, the pH and immobilization time were investigated. The pH and thermal and storage stability of the ANL@PD-MNPs significantly surpassed those of free ANL. The ANL@PD-MNPs had better solvent tolerance than free ANL. The secondary structure of free ANL and ANL@PD-MNPs was analyzed by infrared spectroscopy. A kinetic study demonstrated that the ANL@PD-MNPs had enhanced enzyme-substrate affinity and high catalytic efficiency. The ANL@PD-MNPs was applied as a biocatalyst for the regioselective acylation of dihydromyricetin (DMY) in DMSO and gave a conversion of 79.3%, which was higher than that of previous reports. The ANL@PD-MNPs retained over 55% of its initial activity after 10 cycles of reuse. The ANL@PD-MNPs were readily separated from the reaction system by a magnet. The PD-MNPs is an excellent support for ANL and the resulting ANL@PD-MNPs displayed good potential for the efficient synthesis of dihydromyricetin-3-acetate by enzymatic regioselective acylation

Effects of stocking density and decreased carbon supply on the growth and photosynthesis in the farmed seaweed, Pyropia haitanensis (Bangiales, Rhodophyta)

During seaweed mariculture the stocking density increases with growth season, which would potentially affect the inorganic carbon availability for photosynthesis. In the present study, the red macroalgal species, Pyropia haitanensis, collected from the cultivation site located at Nan'ao Island, Shantou, China (23(o)20'N, 116(o)40'E), was cultured under high and low stocking density level (5 and 1 g L-1) and two different carbon concentrations (ca. 390 and 20 ppm CO2 in air), to investigate how the stocking density and carbon supply affect the growth and photosynthesis of this alga. The relative growth rate (RGR), nitrate reductase (NR) activity, and photosynthetic rates of high stocking density-grown P. haitanensis thalli were decreased compared with low stocking density-grown thalli. The lowered carbon supply in culture inhibited the RGR, NR activity, photosynthetic rates, and photosystem II activity of the algae. It was shown that high stocking density exhibited similar negative effect compared with reduction of carbon supply on the photosynthesis of P. haitanensis. Moreover, high stocking density aggravated the effect resulting from decreased carbon supply on photosynthesis. We proposed that it is necessary to strive to maintain the relative low stocking density to obtain a sustained high rate of biomass increase in P. haitanensis mariculture

Growth and photosynthesis by Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta) in response to different stocking densities along Nan'ao Island coastal waters

Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta) is an important economic seaweed in Southern China. Its use as an alternative source of bioenergy, novel source of bioactives and possible carbon sink has been investigated. The common economic driver of these applications is biomass productivity, which requires an understanding of the effects of different cultivation densities (mat density; 4, 8 and 12 g per cluster) for offshore 'foaling raft' cultivation to maximise productivities. In the present study, the relative growth rate (RGR) and irradiance-saturated maximum photosynthetic rates (P-max) of thalli of G. lemaneiformis grown at high stocking density were lower than those of the algae grown at low stocking density. In three weather types (cloudy, overcast to clear and sunny conditions), the net photosynthetic rates (P-n) of the thalli grown at high stocking density were lower than those of the thalli cultivated at low density. The canopy P-n and increased algal gross biomass of the low-density algal mat were lower than those of the high-density algal mat The increased canopy P-n of G. lemaneiformis in the high-density algal mat decreased under cloudy conditions. We suggest that efforts should be devoted to achieving an appropriate stocking density to obtain a relatively high growth rate, photosynthetic productivity and gross biomass accumulation during G. lemaneiformis maricultivation

Hydrolysis of corn stover pretreated by DESs with carbon-based solid acid catalyst

Abstract This study evaluated two hydrolysis strategies that involve a two-step and a one-pot process for the hydrolysis of cellulose. The two-step process consisted of cellulose pretreatment with deep eutectic solvent, followed by hydrolysis promoted by the carbon-based solid acid catalyst. The obtained results showed that the xylose and glucose yields were 33.9% and 6.9%, respectively, from corn stover based on this two-step strategy with ChCl ·Formic acid used as the pretreatment solvent. For one-pot hydrolysis, side reactions occurred and less glucose accumulated in the reaction system. In this case, the maximum achieved glucose yield was 21.1% for the hydrolysis of microcrystalline cellulose. Graphic abstract The corn stover was pretreated with DES and then hydrolysed by carbon-based solid acid catalyst. Approximately 33.9% of xylose and 6.9% of glucose was recovered from corn stover with ChCl·Formic acid as the pretreatment solvent

Robotic-assisted systems for the safe and reliable treatment of femoral neck fractures: retrospective cohort study

Abstract Background Robots are being used in a wide range of surgical procedures. However, in clinical practice, the efficacy of orthopedic robotic-assisted treatment of femoral neck fractures is still poorly reported, particularly in terms of screw placement accuracy, femoral neck fracture healing rates and postoperative functional recovery. Moreover, there is a lack of comparative analysis between robot-assisted surgery and traditional surgical approaches. Purpose The purpose of this study was to compare the clinical outcomes of patients with femoral neck fractures treated with TiRobot-assisted hollow screw fixation with those of patients with femoral neck fractures treated with traditional surgical approaches. Methods This study included 112 patients with femoral neck fracture who were treated from March 2017 to October 2021 with percutaneous hollow screw internal fixation. These included 56 cases in the TiRobot-assisted surgery group and 56 cases in the standard surgery group. After at least 1 year of follow-up, the treatment outcomes of the two groups were compared, including the amount of intraoperative bleeding, the duration of intraoperative fluoroscopy, the number of guide pin positioning adjustments, the length of hospital stay, the accuracy rate of screw placement, the final Harris Hip Score, the fracture healing rate, and the rate of femoral head necrosis. Statistical analysis software was used to process and analyze the result. Results The TiRobot-assisted group had a statistically significant improvement over the control group in terms of intraoperative bleeding, the duration of intraoperative fluoroscopy, the number of guide pin positioning adjustments, length of hospital stay, accuracy of screw placement and incidence of femoral head necrosis (P  0.05). Conclusion This study shows that TiRobot-assisted surgery has the advantages of short hospital stay, high safety, minimally invasive, high success rate of nail placement, and can reduce the amount of intraoperative radiation and the incidence of femoral head necrosis, thus achieving satisfactory clinical outcomes, and is worthy of clinical promotion

Efficient Hydrolysis of Cellulose over a Novel Sucralose-Derived Solid Acid with Cellulose-Binding and Catalytic Sites

A new sucralose-derived solid acid catalyst (SUCRA-SO₃H), containing −Cl and −SO₃H functional groups, has been shown to be highly effective for hydrolyzing β-1,4-glucans, completely hydrolyzing cellobiose (<b>1</b>) into glucose (<b>2</b>) in 3 h and converting the microcrystalline cellulose pretreated by the ionic liquid into glucose (<b>2</b>) with a yield of around 55% and a selectivity of 98% within 24 h at a relatively moderate temperature (393K). The enhanced adsorption capacity that the catalyst has for glucan by virtue of the presence of chloride groups that act as cellulose-binding sites offers the possibility of resolving the existing bottleneck in heterogeneous catalysis to hydrolyze cellulose, namely, the low accessibility of cellulose to the reaction position in typical solid catalysts. The apparent activation energy for hydrolysis of cellobiose (<b>1</b>) with SUCRA-SO₃H was 94 kJ/mol, which was much lower than that with sulfuric acid (133 kJ/mol) and the corresponding sucrose-derived catalyst (SUCRO-SO₃H) without chlorine groups (114 kJ/mol)

Hydrolase mimic via second coordination sphere engineering in metal-organic frameworks for environmental remediation

Abstract Enzymes achieve high catalytic activity with their elaborate arrangements of amino acid residues in confined optimized spaces. Nevertheless, when exposed to complicated environmental implementation scenarios, including high acidity, organic solvent and high ionic strength, enzymes exhibit low operational stability and poor activity. Here, we report a metal-organic frameworks (MOFs)-based artificial enzyme system via second coordination sphere engineering to achieve high hydrolytic activity under mild conditions. Experiments and theoretical calculations reveal that amide cleavage catalyzed by MOFs follows two distinct catalytic mechanisms, Lewis acid- and hydrogen bonding-mediated hydrolytic processes. The hydrogen bond formed in the secondary coordination sphere exhibits 11-fold higher hydrolytic activity than the Lewis acidic zinc ions. The MOFs exhibit satisfactory degradation performance of toxins and high stability under extreme working conditions, including complicated fermentation broth and high ethanol environments, and display broad substrate specificity. These findings hold great promise for designing artificial enzymes for environmental remediation

Lactiplantibacillus plantarum enables blood urate control in mice through degradation of nucleosides in gastrointestinal tract

Abstract Background Lactobacillus species in gut microbiota shows great promise in alleviation of metabolic diseases. However, little is known about the molecular mechanism of how Lactobacillus interacts with metabolites in circulation. Here, using high nucleoside intake to induce hyperuricemia in mice, we investigated the improvement in systemic urate metabolism by oral administration of L. plantarum via different host pathways. Results Gene expression analysis demonstrated that L. plantarum inhibited the activity of xanthine oxidase and purine nucleoside phosphorylase in liver to suppress urate synthesis. The gut microbiota composition did not dramatically change by oral administration of L. plantarum over 14 days, indicated by no significant difference in α and β diversities. However, multi-omic network analysis revealed that increase of L. plantarum and decrease of L. johnsonii contributed to a decrease in serum urate levels. Besides, genomic analysis and recombinant protein expression showed that three ribonucleoside hydrolases, RihA–C, in L. plantarum rapidly and cooperatively catalyzed the hydrolysis of nucleosides into nucleobases. Furthermore, the absorption of nucleobase by intestinal epithelial cells was less than that of nucleoside, which resulted in a reduction of urate generation, evidenced by the phenomenon that mice fed with nucleobase diet generated less serum urate than those fed with nucleoside diet over a period of 9-day gavage. Conclusion Collectively, our work provides substantial evidence identifying the specific role of L. plantarum in improvement of urate circulation. We highlight the importance of the enzymes RihA–C existing in L. plantarum for the urate metabolism in hyperuricemia mice induced by a high-nucleoside diet. Although the direct connection between nucleobase transport and host urate levels has not been identified, the lack of nucleobase transporter in intestinal epithelial cells might be important to decrease its absorption and metabolization for urate production, leading to the decrease of serum urate in host. These findings provide important insights into urate metabolism regulation. Video Abstrac

Palladium(II)-Catalyzed Enantioselective Arylation of α‑Imino Esters

A protocol for Pd­(II)-catalyzed asymmetric arylation of <i>N</i>-aryl imino esters has been developed. The method affords a practical and direct access to chiral arylglycine derivatives in good yields and with high enantioselectivities