查找使用阿拉丁产品的科研文献

Enhancement of α-ketoisovalerate production by relieving the product inhibition of l-amino acid deaminase from Proteus mirabilis

Shanshan Pei,Xiaobo Ruan,Jia Liu,Wei Song,Xiulai Chen,Qiuling Luo,Liming Liu,Jing Wu

l -Amino acid deaminase (LAAD) is a key enzyme in the deamination of l -valine ( l -val) to produce α-ketoisovalerate (KIV). However, the product inhibition of LAAD is a major hindrance to industrial KIV production. In the present study, a combination strategy of modification of flexible loop regions around the product binding site and the avoidance of dramatic change of main-chain dynamics was reported to reduce the product inhibition. The four mutant PM-LAAD M4 (PM-LAAD S98A/T105A/S106A/L341A ) achieved a 6.2-fold higher catalytic efficiency and an almost 6.7-fold reduction in product inhibition than the wild-type enzyme. Docking experiments suggested that weakened interactions between the product and enzyme, and the flexibility of the “lid” structure relieved LAAD product inhibition. Finally, the whole-cell biocatalyst PM-LAAD M4 has been applied to KIV production, the titer and conversion rate of KIV from l -val were 98.5 g·L −1 and 99.2% at a 3-L scale, respectively. These results demonstrate that the newly engineered catalyst can significantly reduce the product inhibition, that making KIV a prospective product by bioconversion method, and also provide the understanding of the mechanism of the relieved product inhibition of PM-LAAD.

A star-shaped porphyrin-arginine functionalized poly(l-lysine) copolymer for photo-enhanced drug and gene co-delivery

Dong Ma,Qian-Ming Lin,Li-Ming Zhang,Yuan-Yuan Liang,Wei Xue

The co-delivery of drug and gene has become the primary strategy in cancer and other disease therapy. To co-deliver hydrophobic drug and functional gene efficiently into tumor cells, a star-shaped copolymer (PP-PLLD-Arg) with a photochemical internalization effect consisting of a porphyrin (PP) core and arginine-functionalized poly( l -lysine) dendron (PLLD-Arg) arms has been designed, and used to co-deliver docetaxel (DOC) and MMP-9 shRNA plasmid for nasopharyngeal cancer therapy. It was found that PP-PLLD-Arg/MMP-9 nanocomplex showed the photo-enhanced gene transfection efficiency in vitro , and could mediate a significant reduce of MMP-9 protein expression in HNE-1 cells. For co-delivery analysis, the obtained PP-PLLD-Arg/DOC/MMP-9 complexes could induce a more significant apoptosis than DOC or MMP-9 used only, and decreased invasive capacity of HNE-1 cells. Moreover, the star-shaped copolymer exhibited better blood compatibility and lower cytotoxicity compared to PEI-25k in the hemolysis and MTT assays , and also showed a good biocompatibility in vivo . Therefore, PP-PLLD-Arg with suited irradiation is a promising non-toxic and photo-inducible effective drug and gene delivery strategy, which should be encouraged in tumor therapy.

Ultrasound Treatment Improves Fruit Quality of Postharvest Blood Oranges (Citrus sinensis L. Osbeck): Anthocyanin Enrichment and Its Biosynthesis

Jin Chen,Yanru Zhang,Feifei Liu,Jianle Chen,Yujing Sun,Xingqian Ye,Donghong Liu,Huan Cheng

This study was to investigate the effects of different nonthermal treatments on quality attributes, anthocyanin profiles, and gene expressions related to anthocyanin biosynthesis during low-temperature storage, including pulsed light (PL), magnetic energy (ME), and ultrasound (US). Among these treatments, 1 min US treatment was the most effective method for improving fruit quality and increasing total anthocyanin contents (by 29.89 ± 3.32%) as well as individual anthocyanins during low-temperature storage of 28 days. This treatment resulted in high color intensity, intact cellular architectures, and positive sensory evaluation. In contrast, PL and ME treatments displayed negative effects on quality improvement, leading to the destruction of cell architectures and inhibiting anthocyanin levels. Furthermore, qPCR analysis revealed that the structural genes (C4H, CHS1, CHS2, CHI, F3H, ANS, and GST) related to anthocyanin biosynthesis and transport were the target genes and upregulated in response to the cavitation effect of US treatment.

Larvicidal activity of Illicium difengpi BN Chang (Schisandraceae) Stem Bark and its Constituent Compounds against Aedes aegypti L

Y Liu,XC Liu,QY Liu,C Niu,ZL Liu

A Novel Electrochemical Sensor Based on Au-rGO Nanocomposite Decorated with Poly(L-cysteine) for Determination of Paracetamol

Zhang Lin,Si Xiaojing,Yan Xiaoxia,He Haibo,Deng Dongmei,Luo Liqiang

Background: Paracetamol is a common antipyretic and analgesic drug, but its excessive intake can accumulate toxic metabolites and cause kidney and liver damage, so it is critical to determine the content of paracetamol for clinical diagnosis and dose use. Methods: Au-reduced graphene oxide (Au-rGO) nanocomposite decorated with poly(L-cysteine) on carbon paste electrode was fabricated for the determination of paracetamol. Au-rGO was first coelectrodeposited on the carbon paste electrode surface. Afterwards, L-cysteine was electropolymerized to fabricate the Au-rGO/poly(L-cysteine) modified carbon paste electrode. Scanning electron microscope was used to characterize the morphology of Au-rGO and poly(L-cysteine)/Au-rGO. The electrochemical properties of the sensor were studied by cyclic voltammetry and differential pulse voltammetry. Results: After exploring the optimal conditions, the sensor showed a wide linear response for paracetamol detection in the range of 1-200 μM with a detection limit of 0.5 μM (S/N = 3). Conclusion: The fabricated sensor demonstrated good sensitivity with rapid detection capacity in real samples.

A highly sensitive glutamic acid biosensor based on the determination of NADH enzymically generated by L-glutamic dehydrogenase

Xia Lin,Qinghong Wang,Shu Zhu,Juanjuan Xu,Qiao Xia,Yingzi Fu

In this article, a sensitive and stereo-selective biosensor for L-glutamic acid (L-Glu) based on the electrochemiluminescence (ECL) of Ru(bpy)32+ has been designed by applying L-glutamic dehydrogenase (GLDH) for enzymatic generation of NADH in situ. The novel ECL Glu biosensor was prepared by immobilizing GLDH on the modified electrodes with Ru(bpy)32+–platinum nanoparticles (Ru–PtNPs) and reduced graphene oxide–multiwall carbon nanotubes–Nafion (rGO–MWCNT–Nf). Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and cyclic voltammetry (CV) were employed to investigate the characteristics of different materials. In addition, the ECL technology was adopted to explore the interactions between the prepared Glu biosensor and L- or D-Glu. A remarkable difference of ECL intensity was observed when the proposed biosensor interacted with L- and D-Glu, respectively, and good responses were obtained from L-Glu in a range from 1.0 × 10−7 M to 5.0 × 10−3 M with a low detection limit of 3.3 × 10−8 M (S/N = 3). The developed ECL biosensor showed satisfying sensitivity, selectivity, reproducibility and stability, therefore, it might provide a new perspective for the recognition and detection of L-Glu.

Chemical composition and insecticidal properties of the essential oil of Bidens frondosa L (Asteraceae) against booklice (Liposcelis bostrychophila)

Heng Yu Li,Xu Bo Chen,Qi Zhi Liu,Zhi Long Liu

Molecular Basis of Resistance to Bensulfuron-Methyl in a Smallflower Umbrella Sedge (Cyperus difformis L.) Population from China

Shanshan Yin,Wei Hu,Yin Chai,Minghao Jiang,Jingxu Zhang,Haiqun Cao,Ning Zhao,Min Liao

Smallflower umbrella sedge (Cyperus difformisL.) is an invasive weed, and infestations ofC.difformisare increasing in rice (Oryza sativaL.) fields in China. Bensulfuron-methyl is a widely used sulfonylurea herbicide that inhibits the acetolactate synthase (ALS) enzyme and has been used in recent years for effectively controlling annual weeds in the Cyperaceae family. In this study, a suspected resistant population ofC. difformis(BBHY1) was collected from a rice field in Huaiyuan County, Anhui Province, China, that survived treatment with bensulfuron-methyl at the field-recommended rate (FRR). Single-dose tests and whole-plant bioassays confirmed that the BBHY1 population was resistant to bensulfuron-methyl and had evolved a high level of resistance, with a resistance index (RI) of 12.87. Sequencing of theALSgene revealed a CCT to CAT point mutation at codon 197, which caused a P-to-H substitution in the resistant plants. Analysis of the relative expression ofALSrevealed no significant differences between the resistant and susceptible populations. Inhibiting the activity of cytochrome P450s (P450s) or glutathione S-transferases (GSTs) had no significant effect on bensulfuron-methyl resistance. The BBHY1 population exhibited cross-resistance to pyrazosulfuron-ethyl, penoxsulam, and bispyribac-sodium, with RIs ranging from 5.48 to 20.63, but remained susceptible to MCPA sodium, florpyrauxifen-benzyl, and bentazon, with RIs of <1.00. These herbicides could be potentially used as alternatives for controlling resistant populations and managing herbicide resistance in other aggressive weeds in rice fields.Keywords:Cyperus difformis;bensulfuron-methyl;target-site resistance;cross-resistance

Inhibitory effect of ketoconazole, quinidine and 1-aminobenzotriazole on pharmacokinetics of l-tetrahydropalmatine and its metabolite in rats

Weibin Xiao,Zhirong Deng,Chongfa Lai,Haoyang Lu,Mutu Huang,Yuguan Wen,Lei Shi

l-tetrahydropalmatine (l-THP) is mainly metabolised by CYP450 enzymes.This study was to investigate the possible effect of co-administered CYP inhibitors on the pharmacokinetics of l-THP and its metabolites in rats.An established LC-MS/MS method has been applied for the evaluation of drug-drug interaction between l-THP and CYP inhibitors. Following the administration of CYP inhibitors, a single dose of l-THP (9 mg/kg) was orally administrated.With regard to l-THP, the AUC0–48 were significantly increased by 4.3, 3.79, and 11.39 folds, and Cmax were increased by 4.74, 3.64, and 2.76 folds in the ketoconazole group (KET), quinidine group (QD), and 1-aminobenzotriazole group (ABT), respectively. KET and QD both significantly increased the AUC0–48 of 2-DM and 2-DM-Glu by 1.38 ∼ 2.43 times, while Cmax was significantly decreased by 41.3 and 78.0% in the ABT group, respectively. The Cmax of 3-DM was reduced by 51.38, 48.02, and 63.31% after pre-treatment with KET, QD, and ABT, respectively, and Cmax of 3-DM-Glu decreased correspondingly by 29.6, 22.1, and 58.0%.Results indicated that CYP inhibitors could markedly influence the systemic level of l-THP and its metabolites. To guarantee the safe use of l-THP, attention should be paid when l-THP was co-administered with CYP inhibitors, particularly with CYP3A4 and 2D6 inhibitors.

Synthesis of 6-O-Poly(ϵ-caprolactone)-L-ascorbic Acid and its Controlled Release from Supramolecular Polymer Micelles

Feifei Li,Bin Chen,Zhaohua Ping,Xiangxiang Jia,Xin Guo,Longqiang Xiao,Lijian Liu

Lipophilic 6- O -poly ( ϵ -caprolactone)- L -ascorbic acid (AA-6-PCL) is synthesized through ROP of ϵ -caprolactone (CL). The number of repeating CL units in the polymer chain varies from 6 to 19. AA-6-PCL loaded supramolecular polymer micelles (SMPMs) are constructed with β-cyclodextrin (β-CD) and PCL as blocks. Transmission electron microscopy images show a nanospheric morphology of the micelles with a size range of 43.3 ± 5.0 nm. The drug loading contents are 22.53–39.23% for AA-6-PCL. AA-6-PCL exhibits high radical scavenging capacity (93.96–96.73%) and efficient scavenging potency, and a cytotoxicity study proves the excellent cytocompatibility of AA-6-PCL loaded β-CD/PCL SMPMs, which altogether herald their potential application in the study of the induced pluripotent stem cells.

Mitigation of oxidation-induced loss of myofibrillar protein gelling potential by the combination of pyrophosphate and l-lysine

Yungang Cao,Zhaorui Li,Baoling Li,Xin Fan,Miaomiao Liu,Jing Zhao

Protein oxidation, a common quality deterioration in muscle foods, could change the physicochemical characteristics and processability of the meat proteins. The present study focused on the effects of sodium pyrophosphate (PP, 1 mM), Lysine (Lys, 5 mM) and their combination (1 mM PP + 5 mM Lys) on the changes in structure and gelling properties of oxidized myofibrillar protein (Ox-MP). Treatment with the additives modified protein structures, reduced the average particle diameter (d 3,2 and d 4,3 ), restored the gelling behavior of Ox-MP, and remarkably improved the water holding capacity and breaking strength of heat-induced protein gels. The combination of PP and Lys showed a synergistic effect and resulted in the optimal enhancement of Ox-MP gel properties. Specifically, the set gel exhibited a fine, homogeneous and compact microstructure and a breaking strength 4-fold that of Ox-MP. Therefore, a combination of PP and Lys is recommended for aerated meat processing to maintain or enhance the MP gelling potential.

Predicting and Visualizing the Distribution of Cryoprotectant L-Proline in Litopenaeus Vannamei by Machine Learning and Hyperspectral Imaging

Yejun Zhang,Jianan Sun,Jiao Li,Xiangzhao Mao

Cryoprotectants are vital for preserving Litopenaeus vannamei at low temperature, with their penetration in shrimp muscle being crucial for exerting cryoprotective effect. However, traditional methods for detecting cryoprotectants are often destructive, time-consuming, and impractical for real-time applications. To address this limitation, this study proposes a non-destructive approach combining hyperspectral imaging (370–1030 nm) and machine learning for rapid quantification and spatial visualization of cryoprotectant L-Proline in peeled shrimp. Three hundred predictive models were constructed and compared through different preprocessing methods, feature extraction techniques, and algorithms. The optimal model (F-SG-1st-IFS-BP-ANN) achieved a coefficient of determination (R 2 ) of 0.98, a root mean square error (RMSE) of 0.42 mg/g, and a residual prediction deviation (RPD) of 8.06 on the prediction set, with training and prediction times of 0.59 s and 0.0001 s, respectively. Based on this model, the proline distribution within shrimp muscle was clearly visualized, allowing for precise discrimination of concentration gradients. This work demonstrates a novel and efficient strategy for monitoring cryoprotectant diffusion, which can significantly contribute to process optimization and online quality control in the production of frozen shrimp products.