Diversification of Catalytic Function in a Synthetic Family of Chimeric Cytochrome P450s

We report initial characterization of a synthetic family of more than 3000 cytochrome P450s made by SCHEMA recombination of 3 bacterial CYP102s. A total of 16 heme domains and their holoenzyme fusions with each of the 3 parental reductase domains were tested for activity on 11 different substrates. The results show that the chimeric enzymes have acquired significant functional diversity, including the ability to accept substrates not accepted by the parent enzymes. K-means clustering analysis of the activity data allowed the enzymes to be classified into five distinct groups based on substrate specificity. The substrates can also be grouped such that one can be a “surrogate” for others in the group. Fusion of a functional chimeric heme domain with a parental reductase domain always reconstituted a functional holoenzyme, indicating that key interdomain interactions are conserved upon reductase swapping

Hematopoietic and lymphatic cancers in patients with periodontitis : a systematic review and meta-analysis

Numerous studies have explored the correlation of periodontal disease (PD) with risk of hematopoietic and lymphatic cancers, but the findings were inconsistent. Therefore, we did a meta-analysis to ascertain the correlation of PD with risk of incident hematopoietic and lymphatic cancers. The authors searched relevant studies in databases (PubMed, Web of Science, and MEDLINE). The summary relative risk (RR) along with 95% confidence interval (CI) was calculated by use of random or fixed effects models. Six studies were included in qualitative synthesis. The pooled analysis revealed that PD was significantly associated with an increased risk of hematopoietic and lymphatic cancers (RR = 1.17; 95% CI = 1.07?1.27; P = 0). Stratified analysis showed the association of PD with hematopoietic and lymphatic cancers remained significant in the never smokers (RR = 1.28; 95% CI = 1.07?1.54; P = 0.007), and in the American population (RR = 1.17; 95% CI = 1.05?1.30; P = 0.003), respectively. Never smokers population and the American population with PD have a higher risk of developing hematopoietic and lymphatic cancers. PD might be considered as a risk factor for hematopoietic and lymphatic cancers

Electrochemical determination of hydroquinone using hydrophobic ionic liquid-type carbon paste electrodes

Three types of carbon paste electrodes (CPEs) with different liquid binders were fabricated, and their electrochemical behavior was characterized via a potassium hexacyanoferrate(II) probe. 1-Octyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) as a hydrophobic conductive pasting binder showed better electrochemical performance compared with the commonly employed binder. The IL-contained CPEs demonstrated excellent electroactivity for oxidation of hydroquinone. A diffusion control mechanism was confirmed and the diffusion coefficient (D) of 5.05 × 10-4 cm2 s-1 was obtained. The hydrophobic IL-CPE is promising for the determination of hydroquinone in terms of high sensitivity, easy operation, and good durability

An Integration Optimization Strategy of Line Voltage Cascaded Quasi-Z-Source Inverter Parameters Based on GRA-FA

Setting reasonable circuit parameters is an important way to improve the quality of inverters, including waveform quality and power loss. In this paper, a circuit system of line voltage cascaded quasi-Z-source inverter (LVC-qZSI) is built. On this basis, the double frequency voltage ripple ratio and power loss ratio are selected as optimization targets to establish a multi-objective optimization model of LVC-qZSI parameters. To simplify the calculation, an integration optimization strategy of LVC-qZSI parameters based on GRA-FA is proposed. Where, the grey relation analysis (GRA) is used to simplify the multi-objective optimization model. In GRA, the main influence factors are selected as optimization variables by considering the preference coefficient. Then, firefly algorithm (FA) is used to obtain the optimal solution of the multi-objective optimization model. In FA, the weights of objective functions are assigned based on the principle of information entropy. The analysis results are verified by simulation. Research results indicate that the optimization strategy can effectively reduce the double frequency voltage ripple ratio and power loss ratio. Therefore, the strategy proposed in this paper has a superior ability to optimize the parameters of LVC-qZSI, which is of great significance to the initial values setting

Ripple Vector Cancellation Modulation Strategy for Single-Phase Quasi-Z-Source Inverter

The double-frequency (2ω) power flows through the DC side of the single-phase quasi-Z-source inverter (QZSI) leads to the 2ω voltage ripple of capacitors and 2ω current ripple of inductors. This paper proposes a ripple vector cancellation modulation strategy (RVCMS) based on the thought of ripple vector cancellation. By analyzing the mechanism of ripple generation and transmission, we can obtain a variation of a shoot-through duty cycle to generate a compensated 2ω ripple used to cancel the 2ω current ripple of inductors caused by the 2ω ripple of DC link current, and the 2ω compensated variation of a shoot-through duty cycle with a specific amplitude and phase is added to the constant shoot-through duty cycle. Finally, simulation and experimental results demonstrate the correctness and effectiveness of the proposed modulation strategy for the single-phase QZSI

Mechanism Analysis of Sympathetic Inrush in Traction Network Cascaded Transformers Based on Flux-Current Circuit Model

When electric multiple units (EMU) pass the neutral zone, the traction transformer may generate sympathetic inrush, which will cause a malfunction in the transformer differential protection. In order to study the mechanism of the sympathetic inrush of the cascaded traction transformer, the flux–current model of the transformer, line impedance, power system voltage source, and other loads was established. On the basis of the flux–current circuit model, the influence of different factors on the sympathetic inrush of the traction transformer was analyzed. The analysis results were verified by simulation. Research results show that the remanence, closing angle, line impedance, and load will affect the duration and amplitude of the sympathetic inrush

Development of Ecological Fishery in Poyang Lake Area

Through in-depth analysis on history and current situations of fishery development in Poyang Lake area, this paper presents location, resource and environment advantages in development of ecological fishery. According to orientation of leading functions, Poyang Lake can be divided into breeding development, capture operation, enhancement protection and ecological rehabilitation functional zones. In accordance with industrial foundation and ecological advantages of cities and counties in Poyang Lake, it determines the reasonable distribution of 8 leading industries: river crabs, shrimps (Procambarus clarkia), eels, Pengze crucian carp, Siniperca chuatsi, Channa argus, Ietalurus Punetaus, and pearl. On the basis of systematically summing up exploration experience, it comes up with the development path “ecology oriented fishery and industrialization oriented ecological fishery” for ecological fishery in Poyang Lake area. It proposes a series of key technological measures, including reducing fertilizer and drugs, increasing output and benefits, low consumption and emission, high quality and safety, and standardization, to realize a benign cycle of “cost saving, benefit increasing, quality improving and low carbon” and the multi-win objective of coordination between ecology, economy and society

Aggregation-induced fluorescent response of urea-bearing polyphenyleneethynylenes toward anion sensing

A π-conjugated urea-bearing phenyleneethynylene polymer (Poly-2) was rationally designed by the Sonogashira coupling condensation reaction and had been demonstrated to have a unique fluorescent quenching effect for the optical detection of all determined anions, especially for CN−. The fluorescent emission of Poly-2 was significantly quenched upon adding CN−, together accompanied with a continuous red shift of the emission peak from 442 to 464 nm with the cyanide concentration increased from 0 to 1.0 mM. On the contrary, its precursor polymer, Poly-1, itself also displayed fluorescent responsibility with all selected anions but had no obvious selectivity and tendency. For instance, the addition of highly basic CN−, N3−, AcO−, or F− to Poly-1 solution in DMF/H2O (v/v = 1:1) led to the photoluminescence amplification, while the addition of weakly basic anions like Cl−, I−, and Br− showed a fluorescence quenching effect. Both polymers were in a seriously self-aggregated state in solution no matter in the absence or presence of an anion. Interestingly, it was found that Poly-2 exhibited an aggregation-induced emission behavior, while Poly-1 had an aggregation-caused quenching effect, based on the relationship between photoluminescence and polymer aggregation state. The structural characterizations were carried out by NMR spectroscopy and size exclusion chromatography measurements; the photoluminescence properties of Poly-1 and Poly-2 together with anion sensing properties were followed by fluorescence spectroscopy, and the relationship between photoluminescence and aggregation behavior of both polymers in solution was investigated by dynamic light scattering measurements