Evidence for the participation of an extra α-helix at ß-subunit surface in the thermal stability of Co-type nitrile hydratase.

Nitrile hydratase (NHase) has attracted considerable attention since it can efficiently catalyze the hydration of nitriles to valuable amides. However, the poor stability of NHase is one of the main drawbacks in the industrial application. In this study, we compared the structural difference between Fe-type and Co-type NHase and found that an extra α helix existed at the ß-subunit surface of Co-type NHase (defined as the ß-6th helix). Then, the effects of the ß-6th helix were investigated on the thermal stability and the catalytic kinetics of a Co-type NHase from Aurantimonas manganoxydans ATCC BAA-1229 (NHase1229). When the ß-6th helix was deleted or disrupted, the thermal stability of NHase1229 was reduced to 17.6 and 12.9% of that of wild NHase1229, respectively. Thus, the ß-6th helix is important for the thermal stability of Co-type NHase. Based on the structural characteristics of Co-type NHase, the ß-6th helix may be interacted with another helix at the α-subunit (defined as the α-2nd helix) by hydrophobic network just as a "magnetic suction buckle" on the enzyme surface to stabilize the binding of α- and ß-subunits. The ß-6th helix is located at the mouth of the substrate and product tunnel, so it plays crucial roles in catalytic process. Furthermore, the ß-6th helix in NHase1229 was swapped with a thermophilic NHase fragment from Pseudonocardia thermophila JCM3095 (NHase1229-Swap). The thermal stability of NHase1229-Swap was significantly improved, and the half-life was approximately 2.4-fold at 40 °C than that of the wild NHase1229. The knowledge is useful for improving the stability of NHases by restriction fragment swapping.

Swin-Transformer -YOLOv5 for lightweight hot-rolled steel strips surface defect detection algorithm.

An essential industrial application is the examination of surface flaws in hot-rolled steel strips. While automatic visual inspection tools must meet strict real-time performance criteria for inspecting hot-rolled steel strips, their capabilities are constrained by the accuracy and processing speed of the algorithm used to identify defects. To solve the problems of poor detection accuracy, low detection efficiency, and unsuitability of low computing power platforms of the hot-rolled strip surface defect detection algorithm The Swin-Transformer-YOLOv5 model based on the improved one-stage detector is proposed. By employing GhostNet, the model's lightweight design, and guaranteed detection accuracy are both achieved. The C3 module introduces Swin-Transformer to address the issues of cluttered backdrops of defect photos and easily confused defect categories. With the addition of the CoordAttention module, the model's capacity to extract defective features is improved, and its performance keeps getting better. The issue of huge differences in different scales and poor detection of small flaws is resolved by employing BiFPN for feature fusion, and the detector's capacity to adapt to targets of different scales is improved. The experimental results demonstrate that the improved Swin-Transformer-Yolov5 model significantly outperforms the industry-standard target detection algorithms, and the model's mAP value still improves by 8.39% over the original model while reducing the number of parameters, GFLOPs, and weight by 36.6%, 40.0%, and 34.7%, respectively. The model is better suited for use on low-arithmetic platforms as a result.

Plasma pharmacokinetics of melamine and a blend of melamine and cyanuric acid in rainbow trout (Oncorhynchus mykiss).

The objective of the study was to obtain pharmacokinetic parameters for melamine and blend of melamine (MEL) and cyanuric acid (CYA) in rainbow trout (Oncorhynchus mykiss). The single target dosage of MEL (20mg/kg bw) and the blend of MEL and CYA (5 and 1.67 mg/kg bw, respectively) were designed and plasma samples were collected at 30 min, 1, 4, 8, 12, 20, 24, 36, 48, 72, 144 and 240 h sequentially. An optimized method for simultaneous determination of MEL and CYA in plasma and animal tissues by LC-MS/MS was used. The data were shown to best fit a non-compartment model with first order processes of linear characters for melamine, with half-life (t(½)) of 32.2-32.9h, clearance (Cl(z/F)) of 35.9-36.6 ml/h/kg, and volume of distribution (V(ss)) of 1.67-1.74 l/kg. Withdrawal of CYA was much more rapid than that of MEL with higher Cl(z/F) (783.56 ml/h/kg) and shorter t(½) (7.92 h). T(max) of MEL20 and MEL5 were 12 and 20 h, respectively, which showed that T(max) of MEL5 was delayed when MEL and CYA were given together. The results are quite different from those in mammals and showed much slower elimination of MEL and CYA from rainbow trout body.

Study of the effect of membrane thickness on microcapsule strength, permeability, and cell proliferation.

Cell microencapsulation is one of the promising strategies for in vitro production of proteins or in vivo delivery of therapeutic products. Membrane thickness controls microcapsule strength and permeability, which may in return affect cell growth and metabolism. In this study, the strength, permeability, and encapsulated Chinese hamster ovary cell proliferation and metabolism of four groups of microcapsules with different membrane thicknesses were investigated. It was found that increasing membrane thickness increases microcapsule strength, whereas decreases membrane permeability. During the first 6 days, cells within microcapsules with 10 µm thickness membrane proliferated fast and could reach a cell density of 1.9 × 10(7) cells/mL microcapsule with 92% cell density. A cell density of 5.5 × 10(7) cells/mL microcapsule with >85% cell density was achieved within microcapsules with 15 µm membrane thickness and these microcapsules kept over 88% integrity ratio after 11 days, which was much higher than that of microcapsules with 10 µm membrane thickness. Membrane with more than 20 µm thickness was not suited for encapsulated cell culture owing to low-protein diffusion rate. These results indicated that cells survived shortly within the thinnest membrane thickness. There was a specific membrane thickness more suitable for cell growth for a long-time culture. These findings will be useful for preparing microcapsules with the desired membrane thickness for microencapsulated cell culture dependent on various purposes.

Green synthesis of tetrahydrobenzo[b]Pyrans by microwave assisted multi-component one-pot reactions in PEG-400.

Polyethylene glycol is found to be a nontoxic and recyclable reaction medium for the microwave-assisted, multi-component one-pot reactions of aromatic aldehydes with ethyl-2-cyanoacetate and 1,3-cyclohexanedione or 5,5- dimethyl-1,3-cyclohexanedione in the presence of piperidine. This environmentally friendly microwave protocol offers ease of operation and enables recyclability of reaction medium and synthesis of a variety of substituted tetrahydrobenzo[b]pyran derivatives. It is an efficient, promising, and green synthetic strategy to construct tetrahydrobenzo[b]pyran skeleton.