查找使用阿拉丁产品的科研文献

Using galactitol dehydrogenase coupled with water-forming NADH oxidase for efficient enzymatic synthesis of L-tagatose

Wen-Bin Su,Fei-Long Li,Xue-Yong Li,Xiao-Man Fan,Rui-Jiang Liu,Ye-Wang Zhang

L-Tagatose, a promising building block in the production of many value-added chemicals, is generally produced by chemical routes with a low yield, which may not meet the increasing demands. Synthesis of l -tagatose by enzymatic oxidation of d -galactitol has not been applied on an industrial scale because of the high cofactor costs and the lack of efficient cofactor regeneration methods. In this work, an efficient and environmentally friendly enzymatic method containing a galactitol dehydrogenase for d -galactitol oxidation and a water-forming NADH oxidase for regeneration of NAD + was first designed and used for l -tagatose production. Supplied with only 3 mM NAD + , subsequent reaction optimization facilitated the efficient transformation of 100 mM of d -galactitol into l -tagatose with a yield of 90.2 % after 12 h (obtained productivity: 7.61 mM.h −1 ). Compared with the current chemical and biocatalytic methods, the strategy developed avoids by-product formation and achieves the highest yield of l -tagatose with low costs. It is expected to become a cleaner and more promising route for industrial biosynthesis of l -tagatose.

Electrochemical determination of diethylstilbestrol in livestock and poultry meats by L-cysteine/gold nanoparticles modified electrode

Junquan Wu,Xiaojuan Zhao,Yuting Zou,Xiaochun Wu,Weidong Bai,Xiaofang Zeng

A fast and simple electrochemical method for the determination of diethylstilbestrol (DES) was developed. Gold nanoparticles stabilized by chitosan (AuCS) were prepared and used in combination with L-cysteine (L-Cys) by self-assembly for fabricating the electrochemical sensors. Compared with unmodified electrode, the oxidation peak current of DES could be increased greatly by using the L-Cys/AuCS modified GCE (L-Cys/AuCS/GCE), indicating L-Cys/AuCS had excellent ability to promote electron transfer. Under the optimal conditions, the oxidation peak current was linear to the concentration of DES in the range from 5 × 10 −7 to 1 × 10 −4 mol/L (r = 0.997) with the detection limit of 1.7 × 10 −7 mol/L (S/N = 3). The proposed method was successfully used for the determination of DES in livestock and poultry meats with the satisfying recovery results (75.3–91.9%). The method not only exhibited good accuracy and reproducibility for DES detection, but also had the advantages of low cost, simple preparation method and convenient for batch preparation.

Extraction, Radical Scavenging Activities, and Chemical Composition Identification of Flavonoids from Sunflower (Helianthus annuus L.) Receptacles

Zian Qiao,Lu Han,Xinsheng Liu,Huining Dai,Changmin Liu,Min Yan,Wannan Li,Weiwei Han,Xinlu Li,Silu Huang,Bo Gao

This study was focused on extraction, radical scavenging activities, and chemical composition identification of total flavonoids in sunflower (Helianthus annuusL.) receptacles (TFSR). We investigated the optimal extract parameters of TFSR using response surface methodology. The highest yield of TFSR was 1.04% with the ethanol concentration 58%, the material-to-liquid ratio 1:20 (v/w), the extraction time 2.6 h, and the extraction temperature 67 °C. The results of radical scavenging activities showed that ethyl acetate fraction (EAF) was the strongest by using 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2’-azino-bis (3-ethylbenzo thiazoline-6-sulfonic acid) (ABTS) and iron ion reducing analysis. The EAF had the highest flavonoids contents. Four fractions A, B, C and D were enrichment from EAF by polyamide resin. Fraction B had the highest flavonoids content. Thirteen chemical components of flavonoids in fraction B were first identified by Ultimate 3000 Nano LC System coupled to a Q Exactive HF benchtop Orbitrap mass spectrometer (UHPLC-HRMS/MS). Among of the thirteen chemical components, isoquercetin and daidzein were identified accurately by comparing with standard samples. Radical scavenging analysis showed that isoquercetin and EAF had strong activities. Therefore, sunflower receptacles can be used as a source of natural flavonoids. TFSR as a natural radical scavenger has potential applications in pharmaceutical industry.Keywords:sunflower (Helianthus annuusL.);flavonoids;response surface methodology;radical scavenging activities;chemical composition

The Use of Folate/Zinc Supramolecular Hydrogels to Increase Droplet Deposition on Chenopodium album L. Leaves

Yuying Song,Chong Cao,Kaerdun Liu,Jianbin Huang,Li Zheng,Lidong Cao,Fengmin Li,Pengyue Zhao,Qiliang Huang

Pesticide spraying droplets are prone to break and splash when they reach the leaf surface, especially for hydrophobic leaves. The lost pesticide will not deposit on the leaf surface to exert its effect, which eventually enters the environment to cause pollution and even endanger human health. The need to increase spray droplet deposition on plant leaf surfaces has been a great challenge. Many recent studies have increased the deposition of droplets by adding surfactants to spray liquids to reduce surface tension. Here, we propose a carrier system that is a coordination-triggered hierarchical folate/zinc supramolecular hydrogel loaded with pesticide active ingredient to improve the deposition of pesticide droplets. Rather than enhancing deposition by reducing the surface tension like surfactants, the pesticide-loaded folate/zinc hydrogel restricts the movement of liquid droplets through internal cross-linking to form nanofiber networks, thereby suppressing drop broken splashing and bouncing. Morever, the folate/zinc hydrogel is a biocompatible carrier with abundant raw material sources and simple preparation. The research in this paper provides new insights and directions for the study of green pesticide formulations and the enhancement of pesticide droplet deposition.

Communication—Luminescence Properties of a Novel l Rb2KGaF6:Mn4+ Red-Emitting Phosphor for Solid-State Lighting

Dongxin Shi,Xiaoling Xie,Haiqi Pu,Xi Zhang,Qiang Zhou,Zhengliang Wang,Yanqing Ye,Minghong Chen

A novel red-emitting Rb2KGaF6:Mn4+ phosphor with octahedral particulate morphology was presented. The XRD Rietveld refinement results indicate that the phosphor crystallized into the cubic phase of Fm\overline{3}m space group with double perovskite structure. The photo-luminescence spectrum exhibits intense red emission lines with zero-phonon line (ZPL) and v6 peak locating at 620 and 628 nm respectively. The optical parameters of low color temperature (Tc = 3824 K) and high color rendering index (Ra = 90.2 ) from white LED imply its potential application in solid-state lighting.

Development of a dual-fluorescence reporter system for high-throughput screening of L-aspartate-α-decarboxylase

Fei Mingyue,Mao Xudan,Chen Yiyang,Lu Yalan,Wang Lin,Yang Jie,Qiu Juanping,Sun Dongchang

β-Alanine (3-aminopropionic acid) holds great potential in industrial application. It can be obtained through a chemical synthesis route, which is hazardous to the environment. It is well known that l-aspartate-α-decarboxylase (ADC) can convert l-aspartate to β-alanine in bacteria. However, due to the low activity of ADC, industrial production of β-alanine through the green biological route remains unclear. Thus, improving the activity of ADC is critical to reduce the cost of β-alanine production. In this study, we established a dual-fluorescence high-throughput system for efficient ADC screening. By measuring the amount of β-alanine and the expression level of ADC using two different fluorescence markers, we can rapidly quantify the relative activity of ADC variants. From a mutagenesis library containing 2000 ADC variants, we obtained a mutant with 33% increased activity. Further analysis revealed that mutations of K43R and P103Q in ADC significantly improved the yield of β-alanine produced by the whole-cell biocatalysis. Compared with the previous single-fluorescence method, our system can not only quantify the amount of β-alanine but also measure the expression level of ADC with different fluorescence, making it able to effectively screen out ADC variants with improved relative activity. The dual-fluorescence high-throughput system for rapid screening of ADC provides a good strategy for industrial production of β-alanine via the biological conversion route in the future.

Identification of key residues of carboxylesterase PxEst-6 involved in pyrethroid metabolism in Plutella xylostella (L.)

Yifan Li,Hong Sun,Zhen Tian,Yue Li,Xuan Ye,Ruichi Li,Xinyu Li,Shengli Zheng,Jiyuan Liu,Yalin Zhang

The long-term and excessive use of insecticides has led to severe environmental problems and the evolution of insecticide resistance in insects. Carboxylesterases (CarEs) are important detoxification enzymes conferring insecticide resistance on insects. Herein, the detoxification process of Plutella xylostella (L.) carboxylesterase 6 (PxEst-6), one representative P. xylostella carboxylesterase, is investigated with cypermethrin, bifenthrin , cyfluthrin and λ-cyhalothrin. RT-qPCR shows that PxEst-6 is highly expressed in the midgut and cuticles of the third instar larvae. Exposure to pyrethroid insecticides resulted in PxEst-6 up-regulation in a short time. Metabolic assays indicate that PxEst-6 has the capacity to metabolize these pyrethroid insecticides. The combination of molecular docking, binding mode analyses and alanine mutations demonstrated that His451, Lys458 and Gln431 were key residues of PxEst-6 for metabolizing pyrethroids and the acetate groups derived from pyrethroids were key sites for being metabolized by PxEst-6. H451- and K458-derived hydrogen bond (H-bond) interactions with the pyrethroid acetate groups and the polar interactions with the pyrethroid acetate group provided by the Q431 sidechain were crucial to the pyrethroids’ metabolism by PxEst-6. Our study contributes to revealing the reasons for pyrethroid resistance in P. xylostella , and provides a fundamental basis for the development of novel pyrethroid insecticides.

Water-Stable 1D Double-Chain Cu Metal–Organic Framework-based Electrochemical Biosensor for Detecting l-Tyrosine

Xiao-Qin Wu,Pei-Qi Feng,Zhiqiang Guo,Xuehong Wei

An electrochemical biosensor based on a water-stable one-dimensional double-chain Cu(II) metal–organic framework (Cu-MOF) directly was constructed for efficiently recognizing l-tyrosine (l-Tyr) in biomimic environments. Cu-MOF: {[Cu(bpe)(fdc) (H2O)(DMF)]·0.5H2O}n (bpe = 1,2-di(4-pyridyl)ethylene, H2fdc = 2,5-furandicarboxylic acid, namely, Cu-1) was synthesized by a hydrothermal method. It was characterized by IR, scanning electron microscopy, atomic force microscopy, and PXRD techniques. Cu-1 exhibited extreme solvent and thermal stability as well as excellent electroconductive character. It was coated on a glassy carbon electrode (GCE) surface to prepare an electrochemical biosensor (Cu-1/GCE) which showed preferable biosensing ability toward l-Tyr. This Cu-MOF electrochemical biosensor showed simple operation and high sensitivity toward l-Tyr in the concentration range from 0.01 to 0.09 mM. The detection limit is 5.822 μM. Furthermore, Cu-1/GCE showed extremely excellent selectivity to l-Tyr in a biomimic environment with several amino acid interferents. This new strategy exhibits great potential applications for designing MOFs with excellent electrochemical activity.

Ultrasound-assisted aqueous two-phase extraction of synephrine, naringin, and neohesperidin from Citrus aurantium L. fruitlets

Yang Yan,Hui Zhou,Chuanhai Wu,Xiaoye Feng,Chenggang Han,Hao Chen,Yan Liu,Yanfang Li

Toxicity, uptake and transport mechanisms of dual-modal polymer dots in penny grass (Hydrocotyle vulgaris L.)

Jingru Li,Yao Li,Shiyi Tang,Yufan Zhang,Juxiang Zhang,Yuqiao Li,Liqin Xiong

The use of polymers such as plastic has become an important part of daily life, and in aqueous environments, these polymers are considered as pollutants. When macropolymers are reduced to the nanoscale, their small particle size and large specific surface area facilitate their uptake by plants, which has a significant impact on aquatic plants. Therefore, it is essential to study the pollution of nanoscale polymers in the aquatic environment. In this work, we prepared nanoscale polymer dots (Pdots) and explored their toxicity, uptake and transport mechanisms in penny grass. From toxicological studies, in the absence of other nutrients, the cell structure, physiological parameters (total soluble protein and chlorophyll) and biochemical parameters (malondialdehyde) do not show significant changes over at least five days. Through in vivo fluorescence and photoacoustic (PA) imaging, the transport location can be visually detected accurately, and the transport rate can be analyzed without destroying the plants. Moreover, through ex vivo fluorescence imaging, we found that different types of Pdots have various uptake and transport mechanisms in stems and blades. It may be due to the differences in ligands, particle sizes, and oil-water partition coefficients of Pdots. By understanding how Pdots interact with plants, a corresponding method can be developed to prevent them from entering plants, thus avoiding the toxicity from accumulation. Therefore, the results of this study also provide the basis for subsequent prevention work.

Bio-analogue l-lysine lined arrangement on nanofibers with superior proton-conduction for proton exchange membrane

Guodong Zhao,Xianlin Xu,Lei Shi,Bowen Cheng,Xupin Zhuang

Manipulating nanophase-separation behavior and constructing ion-channels is of great challenge for optimizing proton transport. Herein, a novel strategy is demonstrated for constructing long-range and consecutive proton-conducting channels by immobilizing bio-analogue l -lysine onto surface of hydrolyzed polyacrylonitrile (PAN) nanofibers (L/P NFs), combing the superiority of the hydrophilicity 3D network structure (3DNWS) of hydrolyzed PAN NFs and the function of l -lysine as proton-conductors. The hybrid proton exchange membranes (PEMs) are fabricated by filling the inter-fiber voids of L/P NFs with Nafion matrix . The acid–base ion-channels formed between –SO 3 H of Nafion and –NH 2 of L/P NFs may offer the abundant hydrogen-bonded networks for proton hopping. The results show L@Nafion hybrid PEMs can reach 0.263 S/cm (80 °C, 100% relative humidity) proton conductivity and 122.82 mW/cm 2 power density for fuel-cell performance. Besides, the preponderance of 3DNWS of L/P NFs can considerably facilitate the thermal and dimensional stability as well as restrict methanol crossover for hybrid PEMs. This approach brings a unique vision for preparing high-performance PEMs for direct methanol fuel cells.

l-cysteine and 5-norbornene-2-carboxylic acid decorated mesoporous silica spheres as liquid chromatographic material

Fangbin Fan,Xiaobin Nie,Chao Fan,Xiaojing Liang,Xiaofeng Lu,Yong Guo

In this paper, L (+)-Cysteine (L-Cys) and 5-norbornene-2-carboxylic acid (5-N-2-CA) were modified on the silica spheres by cross-linking polymerization and thiol-ene click reaction. The Cys-Si-NCA was characterized by scanning electron microscopy, nitrogen sorption porosimetry , thermogravimetric analysis and other characterization methods. The results indicated that the colume had a regular spherical shape with porous surfaces and particle sizes mainly ranging from 4.5 to 5.5 μm. The surface area of the Cys-Si-NCA microspheres was 328.68 m 2  g −1 , and their respective average pore size was 9.27 nm. Furthermore, the colume exhibited excellent stabilities and reproducibility. Experimental results demonstrate that this new stationary phase can facilitate the separation of sulfonamides, nucleosides and nucleobases compounds in hydrophilic chromatographic (HILIC) conditions. In addition to being able to attenuate the peak tailing of separation, it can also be used for quantitative analysis of creatinine in urine. We also give the temperature and pH ranges of separation on Cys-Si-NCA column. The successful synthesis of the Cys-Si-NCA stationary phase provides foundation for the application of this kind of materials in liquid chromatography (LC).