查找使用阿拉丁产品的科研文献

Electrocatalytic determination of maltol in food products by cyclic voltammetry with a poly(L-phenylalanine) modified electrode

Xinying Ma,Mingyong Chao

Herein, a poly(L-phenylalanine) modified glassy carbon electrode (PLPA/GCE) was fabricated by electrochemical polymerization and a convenient method for the determination of maltol in food products was developed using the fabricated PLPA/GCE. The electrochemical behavior of maltol at the modified electrode was studied by cyclic voltammetry. Experimental results show that the modified electrode exhibits excellent electrocatalytic activity towards the electrochemical oxidation of maltol and the oxidation is a one-proton–one-electron process. In pH 8.0 phosphate buffer solution, the oxidation peak current obtained by cyclic voltammetry is linearly proportional to the concentration of maltol in the range of 8.0 × 10−7 to 5.00 × 10−4 mol L−1 with a limit of detection of 9.5 × 10−8 mol L−1. The stability and reproducibility of the fabricated electrode was evaluated and the performance of the proposed method was validated in terms of linearity (r = 0.9989), recovery (95.2–101.4%), reproducibility (RSD < 3.7%, n = 6) and robustness. The applicability of the developed method has been successfully demonstrated by the determination of maltol in a variety of food products such as cake, beer and red wine.

Feed additive production by fermentation of herb Polygonum hydropiper L. and cassava pulp with simultaneous flavonoid dissolution

Zhen-Tao Song,Ming-Jun Zhu

Fermentation of herb Polygonum hydropiper L. (PHL) and cassava pulp (CP) for feed additive production with simultaneous flavonoid dissolution was investigated, and a two-stage response surface methodology (RSM) based on Plackett−Burman factorial design (PB design) was used to optimize the flavonoid dissolution and protein content. Using the screening function of PB design, four different significant factors for the two response variables were acquired: factors A (CP) and B (PHL) for the flavonoid dissolution versus factors G (inoculum size) and H (fermentation time) for protein content. Then, two RSMs were used sequentially to improve the values of the two response variables separately. The mutual corroboration of the experimental results in the present study confirmed the validity of the associated experimental design. The validation experiment showed a flavonoid dissolution rate of 94.00%, and a protein content of 18.20%, gaining an increase in 21.20% and 199.10% over the control, respectively. The present study confirms the feasibility of feed additive production by Saccharomyces cerevisiae with CP and PHL and simultaneous optimization of flavonoid dissolution and protein content using a two-stage RSM.

Reprogramming the Transition States to Enhance C–N Cleavage Efficiency of Rhodococcus opacus l-Amino Acid Oxidase

Yaoyun Wu,Yaozhong Cui,Wei Song,Wanqing Wei,Zhizhen He,Jinyang Tao,Dejing Yin,Xiulai Chen,Cong Gao,Jia Liu,Liming Liu,Jing Wu

l-Amino acid oxidase (LAAO) is an important biocatalyst used for synthesizing α-keto acids. LAAO from Rhodococcus opacus (RoLAAO) has a broad substrate spectrum; however, its low total turnover number limits its industrial use. To overcome this, we aimed to employ crystal structure-guided density functional theory calculations and molecular dynamic simulations to investigate the catalytic mechanism. Two key steps were identified: S → [TS1] in step 1 and Int1 → [TS2] in step 2. We reprogrammed the transition states [TS1] and [TS2] to reduce the identified energy barrier and obtain a RoLAAO variant capable of catalyzing 19 kinds of l-amino acids to the corresponding high-value α-keto acids with a high total turnover number, yield (≥95.1 g/L), conversion rate (≥95%), and space-time yields ≥142.7 g/L/d in 12–24 h, in a 5 L reactor. Our results indicated the promising potential of the developed RoLAAO variant for use in the industrial production of α-keto acids while providing a potential catalytic-mechanism-guided protein design strategy to achieve the desired physical and catalytic properties of enzymes.

The Glycyrrhiza glabra L. crude extract alleviates lipid accumulation in NAFLD by activating Nrf2 and promoting autophagy

Yunfei Wei,Meiyu Jin,Hao Yu,Xiaoning Hou,Lilei Zhao,Lu Ding,Jiaqi Cheng,Jiazhang Qiu,Haihua Feng

Glycyrrhiza glabra L. is a common heritage herbal medicine rich in antioxidant compounds such as flavonoids and triterpenoids. Non-alcoholic fatty liver disease has been the global prevalent chronic liver disorder. To investigate the curative role and mechanism of the Glycyrrhiza glabra L. crude extract on NAFLD, in vitro , we used oleic acid, palmitic acid, ML-385 and 3-MA to stimulate HepG2 cells. In vivo , we used Tyloxapol to inject mice intraperitoneally to establish an acute model, and high-fat diet to feed wild-type, Nrf2 -/- and ATG5 flox/flox mice to establish a chronic model. We used high performance liquid chromatography to analyse the content of major bioactive components in the Glycyrrhiza glabra L. crude extract. Our study found the Glycyrrhiza glabra L. crude extract could effectively alleviate lipid accumulation in non-alcoholic fatty liver disease, activate Nrf2 and promote autophagy. However, this alleviating effect disappeared when the Nrf2 and autophagy were inhibited separately. Our study demonstrates that crude extraction of active ingredients from traditional herbal medicines may be a potentially inexpensive, rapid and safe approach to alleviate lipid accumulation in non-alcoholic fatty liver disease.

A novel ratiometric fluorescent probe for detection of l-glutamic acid based on dual-emission carbon dots

Lin Yuan,Lizhen Liu,Yunfeng Bai,Jun Qin,Meng Chen,Feng Feng

In this article, we report for the first time the use of a dual-emission carbon dots (CDs) with orange-yellow fluorescence for the detection of l -glutamic acid (L-Glu). The CDs was synthesized through a facile strategy of one-pot hydrothermal route using o -phenylenediamine (oPD) and oxalic acid . The CDs exhibit two fluorescence emission peaks around 453 nm and 560 nm when the excitation wavelength is at 390 nm. In the existence of L-Glu the fluorescence at 560 nm was decreased, whereas the fluorescence at 453 nm was constant. The fluorescence intensity ratio at 560 nm and 453 nm (F 560 /F 453 ) expressed two great linear relationships in the L-Glu concentration range from 0 to 200 μM and 200–400 μM, respectively, with a detection limit (LOD) of about 0.085 μM. In addition, it was used to analyze L-Glu in fetal bovine serum samples successfully, which recoveries were ranging from 97.07 to 103.7%. Those results demonstrate CDs can be further explored in biomedicine studies.

Improved corrosion protective performance of hybrid silane coatings reinforced with nano ZnO on 316 L stainless steel

Mohd Talha,Qi Wang,Mingjie Xu,Yucong Ma,Zhonghui Li,Yuanhua Lin

In this research, silane hybrid coatings based on γ-glycidoxypropyltrimethoxysilane/ methyltrimethoxysilane/ 3-aminopropyl trimethoxysilane (GPTMS/MTMS/ APS) were produce by sol-gel method. ZnO nanoparticles were embedded in the silane coating and this exclusive silane coating was employed to 316 L stainless steel (SS) substrates by the dip-coating method. The surface characteristics of the samples were examined by FTIR analysis, XRD , SEM-EDS, and contact angle measurements. Further, the corrosion protection behavior of the coatings was examined in 3.5 wt% aqueous NaCl solution using potentiodynamic polarization , EIS, and SECM analysis. AFM was applied to determine the surface morphologies of the samples after the polarization test. Our results exhibited that the coatings enhanced the anti-corrosion performance of SS substrates. It was also obtained that the combination of GPTMS/MTMS/APS provided better corrosion protection properties and acts as a strong physical barrier to the corrosive molecules. The presence of nano ZnO further improved the protective barrier of the coating.

l-Tartaric acid tailored polyamide thin-film composite membrane with enhanced performance for salt and molecular removal

Yuhua Xiong,Xingtao Zuo,Jiajie He,Juan Xiong,Cong Ma,Zhongbing Chen,Yun Zhou,Shuili Yu

High performance polyamide (PA) thin-film composite (TFC) membranes are in great demand. However, it is still a challenge to further enable PA TFC membranes to overcome the perm-selectivity tradeoff. Here, l -tartaric acid (LTA) and piperazine were first used as the aqueous phase monomers to fabricate LTA integrated PA (LTA/PA) TFC membranes via interfacial polymerization (IP) with trimesoyl chloride. The physicochemical property and separation performance of the PA TFC membranes were regulated via LTA concentrations. The introduction of LTA made the PA layer of the membrane thinner and smoother with enlarged pore size. The LTA/PA TFC membrane prepared with a higher LTA content had a maximal water flux (207.6 LMH/bar, 20 times higher than that of the control membrane), with superior rejections for the dyes (>98.0 %) and low removal rates for the salts (<4.5 %). Of note, the water flux of the membrane prepared with a low LTA content was enhanced to 18.9 LMH/bar without sacrificing the rejection of Na 2 SO 4 ( R Na 2 SO 4  > 98.0 %). The membranes with optimal LTA content break the tradeoff towards some dyes or salts, and presented superior performance compared with most other reported polymeric membranes. This work highlights the great potential of constructing natural acid-modulated PA composite membranes in water purification .

Ambient Hydrogen Storage and Release Using CO2 and an l-Arginine-Functionalized PdAu Catalyst via pH Control

Shuchao Jiang,Junxia Yang,Shengliang Zhai,Ling Zhang,Rui Tu,Tie Yu,Dong Zhai,Lei Sun,Weiqiao Deng,Guoqing Ren

Formic acid (FA)/formate as a promising liquid organic hydrogen carrier exhibits great potential for future energy supplies. However, FA/formate-based hydrogen storage and release, which can be operated under ambient conditions, is challenging but attractive. Here, we report an ambient hydrogen storage and release process that uses the acidity and alkalinity of the reaction solution to control hydrogen production or consumption via an l-arginine-functionalized active carbon-supported PdAu alloy catalyst (PdAu/AC-LA). By regulating the LA loading and Pd/Au ratio, we obtain the optimal catalytic activity with turnover frequency (TOF) of 1760 h–1 for FA dehydrogenation under acidic conditions and 138 h–1 for CO2 hydrogenation under alkaline conditions. Comprehensive characterizations, including X-ray photoelectron spectroscopy (XPS), CO2 temperature-programmed desorption (CO2-TPD), and HCOO– adsorption experiments, reveal that the synergistic effect between PdAu alloy and strongly basic l-arginine enhances catalytic activity by regulating the adsorption of reactants. Our work, as a successful example of FA/formate-based hydrogen storage and release under ambient conditions, may aid putting the safe and energy-saving use of hydrogen into practice.

Self-assembly of L-cysteine–gold nanoparticles as chiral probes for visual recognition of 3,4-dihydroxyphenylalanine enantiomers

Lin Zhang,Chunli Xu,Guoxin Song,Baoxin Li

A simple protocol to distinguish enantiomers is extremely intriguing and useful. Herein, we report on a method for the visual recognition of 3,4-dihydroxyphenylalanine (Dopa) enantiomers. It is based on the chirality of L-cysteine-capped gold nanoparticles (L-Cys-capped AuNPs) that can be used as a chiral selector for L- and D- forms of Dopa. On addition of L-Dopa to a solution of the L-Cys-capped AuNPs, a color change from red to blue can be seen, while no color change is found on addition of D-Dopa. The chiral recognition can be achieved by eye and simple spectrophotometry. Notably, this method does not require complicated chiral modification. The method excels through its low-cost, good availability of materials, and its simplicity.

A novel electrochemical sensor based on Fe2O3 nanoparticles/N-doped graphene for electrocatalytic oxidation of L-cysteine

Yang Suling,Li Gang,Wang Guifang,Deng Dehua,Qu Lingbo

A novel electrochemical sensor based on Fe 2 O 3 nanoparticles supported on N-doped graphene (Fe 2 O 3 NPs/N–GR) has been fabricated for electrocatalytic oxidation and detection of L-cysteine. The Fe 2 O 3 NPs/N–GR was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and electrochemical methods. The electrochemical behavior of L-cysteine at Fe 2 O 3 NPs/N–GR was investigated by voltammetry. The Fe 2 O 3 NPs/N–GR showed a very efficient electrocatalytic activity for the oxidation of L-cysteine in 0.1 M phosphate buffer solution (PBS, pH 7.0). The oxidation peak currents increased dramatically at Fe 2 O 3 NPs/N–GR-modified electrode. The potential utility of the sensor was demonstrated by applying it to the analytical determination of L-cysteine. Experimental results showed that the electrocatalytic current increased linearly with L-cysteine concentration in the range of 0.2–400 μM with a lowest detectable concentration of 0.1 μM.

Enrichment and Purification of the Bioactive Flavonoids from Flower of Abelmoschus manihot (L.) Medic Using Macroporous Resins

Zhenzhong Yang,Haitao Tang,Qing Shao,Anna Rita Bilia,Yi Wang,Xiaoping Zhao

Flower ofAbelmoschus manihot(FAM) is clinically effective to treat chronic kidney disease (CKD) with a relatively high dosage. To improve the efficacy and the compliance of patients, macroporous resins were adopted to enrich and purify flavonoids from FAM, which are thought to be the major renal protective constituents in FAM. After screening six different kinds of macroporous resins, HPD-100 was selected for its great adsorption and desorption capacity. Then, orthogonal design tests were used to optimize parameters in the processes of impurity removal and flavonoids of FAM desorption on column chromatogram. Moreover, process scale-up was performed, and purification effects maintained after amplification. After purification, the content of seven main flavonoids in the product increased from 8.29% to 51.43%. Protective and anti-inflammatory effects of crude extract and the flavonoid component of FAM after purification were investigated on the adriamycin-damaged HK-2 cells and lipopolysaccharide-stimulated Raw 264.7 cells models. Both bioactivities were improved greatly after purification for these two cell models. Therefore, the purification process had enriched the main bioactive constituents with potential alleviating kidney injury activities. The flavonoid component of FAM is worthy of being developed as an improved remedy for CKD with better patients’ compliance.Keywords:Abelmoschus manihotflowers;macroporous resins;flavonoids

Investigation of silk fibroin nanoparticle-decorated poly(l-lactic acid) composite scaffolds for osteoblast growth and differentiation

Biao-Qi Chen,Ranjith Kumar Kankala,Ai-Zheng Chen,Ding-Zhu Yang,Xiao-Xia Cheng,Ni-Na Jiang,Kai Zhu,Shi-Bin Wang