Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 4.244
Filtrar
1.
Phys Chem Chem Phys ; 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33000818

RESUMO

The lack of high-performance anode materials has become a major obstacle to the development of Li- and Na-ion batteries. Recently, 2D transition metal borides (e.g. MBenes) have attracted much attention due to their excellent stability and electrical conductivity. Unfortunately, most of the reported MBene phases typically have an intrinsic metal-rich structure with metal atoms exposed on the surface, which harmfully affect the adsorption of Li/Na atoms. Here, through crystal structure prediction combined with the first-principles density functional theory, a novel TiB3 MBene has been determined by altering the proportion of non-metallic element boron to wrap metal atoms and weaken nearest-neighbor electrostatic repulsion. Electrostatic potential analysis visually shows a surface with low potential on the TiB3 monolayer implying high adsorption capacity, and also can be used to quickly screen out the Li/Na adsorption sites. Accurate half-cell battery simulation confirmably shows that the TiB3 monolayer possesses a theoretical specific capacity of 1335.04 and 667.52 mA h g-1 for Li and Na, respectively. The TiB3 monolayer can remain metallic after adsorbing Li/Na atoms, which ensures good conductivity during battery cycling. The ultra-low barrier energy (only 38 meV for Li) and suitable open-circuit voltage indicate excellent charging and discharging capabilities. These results suggest that the TiB3 monolayer could be a promising anode material for Li- and Na-ion batteries, and provide a simple design principle for exposing non-metallic atoms on the surface.

2.
Mol Psychiatry ; 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33005027

RESUMO

Fear and anxiety are two defensive emotional states evoked by threats in the environment. Fear can be initiated by either imminent or future threats, but experimentally, it is typically studied as a phasic response initiated by imminent danger that subsides when the threats is removed. In contrast, anxiety is a sustained response, initiated by imagined or potential threats. The central amygdala (CeA) is a key structure active during both fear and anxiety but thought to engage different neural systems. Fear responses are triggered by activation of somatostatin (SOM) expressing neurons in the lateral division of the CeA (CeL), and downstream projections from the medial division. Anxiety responses engage the central extended amygdala that includes the CeA, central sublenticular extended amygdala (SLEAc) and bed nucleus of the stria terminalis, but the nature of connections between these regions is not understood. Here using a combination of tract tracing, electrophysiology, and behavioral analysis in mice, we show that a population of SOM+ neurons in the CeL project to the SLEAc where they inhibit local GABAergic interneurons. Optogenetic activation of this input to the SLEAc has no effect on movement, but is anxiogenic in both open field and elevated plus maze. Our results define the inhibitory connections between CeL and SLEAc and establish a specific CeL to SLEAc projection as a circuit element in mediating anxiety.

3.
Phytother Res ; 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-33006176

RESUMO

Rheumatoid arthritis (RA) is a chronic autoimmune disease that affects not only joints but also multiple organ systems including cardiovascular system. Endothelial dysfunction plays an important role in cardiovascular diseases (CVD). In RA, endothelial dysfunction exists at both the macrovascular and the microvascular levels, which is a precursor to vasculitis. This study aimed to investigate the pathogenesis of vasculitis and the therapeutic effect of CP-25 on vasculitis in high-fat diet (HFD) collagen-induced arthritis (CIA) rats. Experimental groups were divided into normal group, HFD group, CIA group, HFD CIA group, CP-25 group and MTX group. In vitro, IL-17A was used to stimulate human umbilical vein endothelial cells (HUVECs), and then CP-25 was used to intervene. Results showed that CP-25 reduced global scoring (GS), arthritis index (AI), and swollen joint count (SJC) scores, improved histopathological score, reduced T cells percentage, and decreased IL-17A and ICAM-1 levels. Besides, CP-25 reduced the expression of p-STAT3 to normal levels in vascular of HFD CIA rats. In vitro, IL-17A promoted the expression of p-JAK1, p-JAK2, p-JAK3, pSTAT3, and ICAM-1, and CP-25 inhibited the expression of p-JAK1, p-JAK2, p-JAK3, p-STAT3, and ICAM-1. In conclusion, CP-25 might inhibit endothelial cell activation through inhibiting IL-17A/JAK/STAT3 signaling pathway, which improves vasculitis in HFD CIA rats.

4.
Cell Oncol (Dordr) ; 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-33006750

RESUMO

PURPOSE: Stemming from a myriad of genetic and epigenetic alterations, triple-negative breast cancer (TNBC) is tied to poor clinical outcomes and aspires for individualized therapies. Here we investigated the therapeutic potential of co-inhibiting integrin-dependent signaling pathway and BRD4, a transcriptional and epigenetic mediator, for TNBC. METHODS: Two independent patient cohorts were subjected to bioinformatic and IHC examination for clinical association of candidate cancer drivers. The efficacy and biological bases for co-targeting these drivers were interrogated using cancer cell lines, a protein kinase array, chemical inhibitors, RNAi/CRISPR/Cas9 approaches, and a 4 T1-Balb/c xenograft model. RESULTS: We found that amplification of the chromosome 8q24 region occurred in nearly 20% of TNBC tumors, and that it coincided with co-upregulation or amplification of c-Myc and FAK, a key effector of integrin-dependent signaling. This co-upregulation at the mRNA or protein level correlated with a poor patient survival (p < 0.0109 or p < 0.0402, respectively). Furthermore, we found that 14 TNBC cell lines exhibited high vulnerabilities to the combination of JQ1 and VS-6063, potent pharmacological antagonists of the BRD4/c-Myc and integrin/FAK-dependent pathways, respectively. We also observed a cooperative inhibitory effect of JQ1 and VS-6063 on tumor growth and infiltration of Ly6G+ myeloid-derived suppressor cells in vivo. Finally, we found that JQ1 and VS-6063 cooperatively induced apoptotic cell death by altering XIAP, Bcl2/Bcl-xl and Bim levels, impairing c-Src/p130Cas-, PI3K/Akt- and RelA-associated signaling, and were linked to EMT-inducing transcription factor Snail- and Slug-dependent regulation. CONCLUSION: Based on our results, we conclude that the BRD4/c-Myc- and integrin/FAK-dependent pathways act in concert to promote breast cancer cell survival and poor clinical outcomes. As such, they represent promising targets for a synthetic lethal-type of therapy against TNBC.

5.
Eur Radiol ; 2020 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-33025175

RESUMO

OBJECTIVES: We aimed to determine the value of MR-based preoperative nomograms in predicting DNA copy number (CN) subtype in lower grade glioma (LGG) patients. METHODS: The overall survival (OS) data were analyzed. MRI data of 170 subjects were retrospectively analyzed. The correlation was explored by univariate and multivariate regression analysis. RESULTS: CN2 subtype was associated with shortest median OS (CN2 subtype vs. others: 46.8 vs. 221.7 months, p < 0.05). The time-dependent receiver operating characteristic for the CN2 subtype was 0.80 (95% CI: 0.74-0.85) for survival at 1 year, 0.80 (95% CI: 0.75-0.85) for survival at 2 years, and 0.77 (95% CI: 0.73-0.83) for survival at 3 years. On multivariate analysis, hemorrhage (OR: 0.118; p < 0.001; 95% CI: 0.037-0.376), poorly defined margin (OR: 4.592; p < 0.001; 95% CI: 1.965-10.730), extranodular growth (OR: 0.247; p = 0.006; 95% CI: 0.091-0.671), and volume ≥ 60 cm3 (OR: 4.734.256; p < 0.001; 95% CI: 2.051-10.924) were associated with CN1 subtype (AUC: 0.781). Proportion CE tumor (OR: 5.905; p = 0.007; 95% CI: 1.622-21.493), extranodular growth (OR: 9.047; p = 0.001; 95% CI: 2.349-34.846), width ≥ median (OR: 0.231; p = 0.049; 95% CI: 0.054-0.998), and depth ≥ median (OR: 0.192; p = 0.023; 95% CI: 0.046-0.799) were associated with CN2 subtype (AUC: 0.854). Necrosis/cystic (OR: 6.128; p = 0.007; 95% CI: 1.635-22.968), hemorrhage (OR: 5.752; p = 0.002; 95% CI: 1.953-16.942), poorly defined margin (OR: 0.164; p < 0.001; 95% CI: 0.063-0.427), and volume ≥ median (OR: 4.422; p < 0.001; 95% CI: 1.925-10.160) were associated with CN3 subtype (AUC: 0.808). All three nomograms showed good discrimination and calibration. Decision curve analysis supported that all nomograms were clinically useful. The average accuracy of the tenfold cross-validation was 0.680 (CN1), 0.794 (CN2), and 0.894 (CN3), respectively. CONCLUSIONS: The shortest OS was observed in patients with CN2 subtype. This preliminary radiogenomics analysis revealed that the MR-based preoperative nomograms provide individualized prediction of DNA copy number subtype in LGG patients. KEY POINTS: • This preliminary radiogenomics analysis of LGG revealed that the MR-based preoperative nomograms provide individualized prediction of DNA copy number subtype in LGG patients. • The AUC for the ROC curve was 0.781 for CN1 subtype, 0.854 for CN2 subtype, and 0.808 for CN3 subtype. Decision curve analysis supported that all nomograms were clinically useful. • The sensitivity was 0.779 (CN1), 0.731 (CN2), and 0.851 (CN3), respectively. The specificity was 0.664 (CN1), 0.872 (CN2), and 0.625 (CN3), respectively. And the accuracy was 0.717 (CN1), 0.849 (CN2), and 0.692 (CN3), respectively.

6.
Nanoscale ; 2020 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-33020780

RESUMO

By using metal compounds or oxide/organic acid and enhanced reaction temperatures in the controlled solvothermal oxidation of [Mo3O2(MeCO2)6(H2O)3]2+, more interstitial metal atoms were introduced to produce the largest nanoscale MoIV-polyoxomolybdates, [M2@(MoIV3py3)4Mo18Ox]q- (M = Al, V, Mo). Each [H4V2@(MoIV3py3)4Mo18O84]12- (2a) nanocluster is surrounded by 12 [V3Mo12O42] to build a Lewis catalysis field (LCF) composed of MoIV3[O8Mo4]3 Lewis acid-base cluster pairs in the crystalline 2, accounting for the excellent and stable catalysis performance in the hydrazine reduction of nitroarenes to arylamines in varied solvents. The proposed new concept LCF provides a new way of thinking for designed synthesis and real applications of highly efficient LCF catalysts.

7.
ACS Nano ; 2020 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-33016697

RESUMO

Tumor accumulation and intratumoral singlet oxygen (1O2) generation efficiency of photosensitizers (PSs) are two essential factors that determine their photodynamic therapy (PDT) efficacies. How to maximize the PS performance at the tumor site is of great research interest. Herein, we report a metal-organic framework (ZIF-8, ZIF = zeolitic imidazolate framework) assisted in vivo self-assembly nanoplatform, ZIF-8-PMMA-S-S-mPEG, as an effective tool for organic PS payloads to achieve efficient PDT. Using an organic PS with aggregation-induced emission as an example, under intratumoral bioreduction, PS-loaded ZIF-8-PMMA-S-S-mPEG (PS@ZIF-8-PMMA-S-S-mPEG) was self-assembled into large ordered hydrophobic clusters, which greatly enhance tumor retention and accumulation of the PS. Moreover, hydrophobic ZIF-8 assemblies greatly isolate the loaded PSs from water and improve O2 transport for the PSs to effectively produce 1O2 inside tumors under light irradiation. The organic PS is therefore endowed with optimal tumor accumulation and intratumoral 1O2 production, demonstrating the effectiveness of the developed self-assembly strategy in PDT application.

8.
Biochim Biophys Acta Gene Regul Mech ; 1863(12): 194641, 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-33017669

RESUMO

Phase separation is the basis for the formation of membrane-less organelles in cells and is involved in many biological processes. Many biological macromolecules, such as proteins and nucleic acids, exert their biological functions by forming phase-separated condensates, and phase separation is closely related to various human diseases. Gene transcriptional regulation is an indispensable part of gene expression and normal function in cells. Its abnormal regulation often causes the occurrence of different diseases. In recent years, the occurrence of phase separation during transcriptional regulation has become an area of intense research. This review summarizes the process of phase separation involved in heterochromatin formation and chromatin remodeling, transcriptional regulation and post-transcriptional regulation. It provides a reference for understanding gene regulation during cell identity and disease development.

9.
BMC Pulm Med ; 20(1): 266, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-33059643

RESUMO

BACKGROUND: Recently, long non-coding RNAs (lncRNAs) have been reported to be involved in regulating chemo-resistance of NSCLC, however, the role of lncRNA SNHG14 in the DDP-resistance of NSCLC remains unexplored. METHODS: Relative expression of SNHG14, HOXB13 and miR-133a in DDP-resistant A549 (A549/DDP) cell and its parental cell A549 were measured using qRT-PCR. Cell proliferation viability of indicated A549/DDP cell was estimated via CCK-8 and colony formation experiments. Cell cycle and apoptosis were analyzed through flow cytometry. Expression of apoptosis-related protein and HOXB13 were detected via western blot. The interaction among SNHG14, HOXB13 and miR-133a was predicted by bioinformatics and validated by dual-luciferase reporter assay. RESULTS: LncRNA SNHG14 and HOXB13 were upregulated while miR-133a was downregulated in A549/DDP cell line compared to A549 cell line. SNHG14 knockdown or miR-133a overexpression was demonstrated to increase the DDP-sensitivity of A549/DDP cells. SNHG14 was revealed to compete with HOXB13 for miR-133a binding in A549/DDP cells. Inhibition of miR-133a in A549 cells could reverse the promotive effects of SNHG14 knockdown on DDP-sensitivity, as well as the inhibitory effects on HOXB13 expression. HOXB13 overexpression was revealed to abolish the enhanced effects of miR-133a on the sensitivity of A549/DDP cell to DDP. CONCLUSION: Our findings demonstrated that SNHG14 was involved in the development of DDP-resistance of A549/DDP cells through miR-133a/HOXB13 axis, which may present a path to novel therapeutic stratagems for DDP resistance of NSCLC.

10.
Chem Biodivers ; 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-33063468

RESUMO

This study aimed to investigate the metabolic effects of endophytic fungi in Gentiana rigescens . From the 100 selected morphospecies , strain 7-2 ( Penicillium brasilianum ) showed a remarkable biocatalytic activity for gentiopicroside and swertiamarin, yielding seven products, including one new compound, 5-ethylidene-8-hydroxy-4,5,6,8-tetrahydropyrano[3,4- c ]-pyran-1-one ( M04 ), alongside six known compounds. gentianine ( M01 ) was the only metabolite of swertiamarin in this study, while the remaining ones were all gentiopicroside metabolites . Among these, five compounds : gentianine ( M01 ), 5 α -(hydroxymethyl)-6 ß -methyl-1 H ,3 H -5,6-dihydropyrano[3,4- c ]pyran-1(3 H )-one ( M02 ), 5 α -(hydroxymethyl)-6 α -methyl-5,6-dihydropyrano[3,4- c ]pyran-1(3 H )-one ( M03 ), 2-(3-formyl-2-oxo-3,6-dihydro- 2H -pyran-4-yl)-but-3-enoic acid ( M06 ), and 2-oxo-4-(1-oxobut-3-en-2-yl)-3,6-dihydro- 2H -pyran-3-carboxylic acid ( M07 ) were similar to gentiopicroside metabolites in humans. Screening the metabolic potential of endophytic fungi in Gentiana rigescens provides an outstanding source for assessing the bioactive metabolites of iridoid glycosides. The above findings suggested that the endophytic fungi of G. rigescens possess multi-enzyme systems that mimic metabolic reactions in mammalian organisms.

12.
Technol Cancer Res Treat ; 19: 1533033820963662, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33034276

RESUMO

PURPOSE: The purpose of this study was to investigate the clinical efficacy of salvage percutaneous radiofrequency ablation in patients with unresectable colorectal cancer liver metastases. METHODS: The cohort consisted of 81 patients with 126 colorectal cancer liver metastases who underwent radiofrequency ablation between January 2012 and September 2016. The clinical data and ablation data were retrospectively analyzed. The local tumor progression-free survival, overall survival, and prognostic factors were analyzed using the log-rank test and Cox regression model. RESULTS: The technique success rate was 99.21%. The primary efficacy rate was 100% at the 1-month follow-up. Minor complications were observed in 2 patients, which recovered within 1 week. The median local tumor progression-free survival time of all patients was 29.8 months. The absence of subsequent chemotherapy was an independent predictor of a shorter local tumor progression-free survival time (P < 0.001, hazard ratio: 2.823, 95% confidence interval: 1.603, 4.972). The median overall survival time was 26.8 months. A lesion size greater than 3 cm (P = 0.011, hazard ratio: 2.112, 95% confidence interval: 1.188, 3.754) and the presence of early local tumor progression (P = 0.011, hazard ratio: 2.352, 95% confidence interval: 1.217, 4.545) were related to a shorter survival time. CONCLUSIONS: Percutaneous radiofrequency ablation is safe in patients with colorectal cancer liver metastases refractory from chemotherapy. Subsequent chemotherapy is important to enhance local control. Small lesions and favorable early responses are related to prolonged overall survival.

13.
Mol Cell Proteomics ; 2020 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-33077686

RESUMO

Esophageal squamous cell cancer (ESCC) is an aggressive malignancy with poor therapeutic outcomes. However, the alterations in proteins and post-translational modifications (PTMs) leading to the pathogenesis of ESCC remains unclear. Here, we provide the comprehensive characterization of the proteome, phosphorylome, lysine acetylome and succinylome for ESCC and matched control cells using quantitative proteomic approach. We identify abnormal protein and post-translational modification (PTM) pathways, including significantly downregulated lysine succinylation sites in cancer cells. Focusing on hyposuccinylation, we reveal that this altered PTM was enriched on enzymes of metabolic pathways inextricably linked with cancer metabolism. Importantly, ESCC malignant behaviors such as cell migration are inhibited once the level of succinylation was restored in vitro or in vivo This effect was further verified by mutations to disrupt succinylation sites in candidate proteins. Meanwhile, we found that succinylation has a negative regulatory effect on histone methylation to promote cancer migration. Finally, hyposuccinylation is confirmed in primary ESCC specimens. Our findings together demonstrate that lysine succinylation may alter ESCC metabolism and migration, providing new insights into the functional significance of PTM in cancer biology.

14.
Intern Emerg Med ; 2020 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-33078224

RESUMO

Chronic kidney disease (CKD) significantly increases the rate of adverse cardiovascular events in patients with coronary artery disease. In this study, we aimed to establish a risk score (RS) model to predict in-hospital mortality risk in patients with end-stage renal disease (ESRD) and acute myocardial infarction (AMI). A total of 113 consecutive patients with ESRD and AMI were retrospectively enrolled between January 1, 2015 and December 31, 2019. All patients received regular hemodialysis and were divided into two groups according to the prognosis during hospitalization. Univariable and multivariable logistic regression analyses were used to identify the risk factors of in-hospital mortality. A RS model was developed based on multiple regression analysis and was internally validated using 1000 bootstrap analysis. The receiver operating characteristic (ROC) curve was performed, and the area under curve (AUC) was analyzed to evaluate the performance of the RS model. AUCs were compared using the Z test. Thirty-three patients died during hospitalization, resulting in in-hospital mortality rate of 29.2%. After multivariate logistic regression, an RS model (0-8) was established based on five independent factors that were assigned with different points according to relative coefficients (coefficient of the index risk factor divided by the lowest coefficient among these five risk factors; rounded to closest integer): 1 for C-reactive protein (CRP) ≥ 14.2 mg/L and left ventricular ejection fraction (LVEF) ≤ V3%; 2 for age ≥ 65 years old, heart rate (HR) at admission ≥ 86 beats per minute (bpm) and D-dimer ≥ 2.4 mg/L FEU. The present RS model had a sensitivity of 85.7%, the specificity of 84%, and an accuracy of 78.1%. In ROC curve analysis, the model demonstrated a good discriminate power in predicting in-hospital mortality (AUC = 0.895, 95% CI 0.814-0.96; P < 0.001), which was significantly better than the predictive power of the Global Registry of Acute Coronary Events risk score (GRACE RS) (AUC = 0.754, 95% CI 0.641-0.868; P < 0.001 after Z test). A novel RS model, which was established to help predict in-hospital mortality of patients with ESRD and AMI, was easy to use and had higher accuracy than the GRACE RS.

15.
Cell Biol Toxicol ; 2020 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-33040242

RESUMO

Cadmium (Cd), a highly toxic heavy metal, is widespreadly distributed in the environment. Chronic exposure to Cd is associated with the development of several diseases including cancers. Over the decade, many researches have been carried on various models to examine the acute effects of Cd; yet, limited knowledge is known about the long-term Cd exposure, especially in the human lung cells. Previously, we showed that chronic Cd-exposed human bronchial epithelial BEAS-2B cells exhibited transformed cell properties, such as anchorage-independent growth, augmented cell migration, and epithelial-mesenchymal transition (EMT). To study these Cd-transformed cells more comprehensively, here, we further characterized their subproteomes. Overall, a total of 63 differentially expressed proteins between Cd-transformed and passage-matched control cells among the five subcellular fractions (cytoplasmic, membrane, nuclear-soluble, chromatin-bound, and cytoskeletal) were identified by mass spectrometric analysis and database searching. Interestingly, we found that the thiol protease ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1) is one of the severely downregulated proteins in the Cd-transformed cells. Notably, the EMT phenotype of Cd-transformed cells can be suppressed by forced ectopic expression of UCHL1, suggesting UCHL1 as a crucial modulator in the maintenance of the proper differentiation status in lung epithelial cells. Since EMT is considered as a critical step during malignant cell transformation, finding novel cellular targets that can antagonize this transition may lead to more efficient strategies to inhibit cancer development. Our data report for the first time that UCHL1 may play a function in the suppression of EMT in Cd-transformed human lung epithelial cells, indicating that UCHL1 might be a new therapeutic target for chronic Cd-induced carcinogenesis. Graphical abstract.

16.
Chemosphere ; 264(Pt 1): 128430, 2020 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-33002801

RESUMO

Non-thermal plasma (NTP) has developed into an emerging end-of-pipe technology for treating volatile organic compounds (VOCs) present in unhygienic point source of air streams. In this work, NTP oxidation of low-concentration ethyl acetate was performed in a coaxial double dielectric barrier discharge reactor. The effects of initial ethyl acetate concentration, gas flow rate, and external electrode length on ethyl acetate degradation were systematically investigated as a function of discharge power. In addition, detailed real-time and online proton transfer reaction mass spectrometry analysis was used to identify the transient species formation and transition in the various NTP oxidation periods of ethyl acetate. Based on the analysis of organic by-products, the degradation mechanism was speculated and the major reaction channels were presented. This study would deepen the understanding of plasma degradation of VOCs and reveal the plasma-chemical mechanism.

17.
PLoS One ; 15(10): e0240238, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33064720

RESUMO

Regional differences and regulatory mechanisms of vegetation productivity response to changing environmental conditions constitute a core issue in macroecological researches. To verify the main limiting factors of different macrosystems [temperature-limited Tibetan Plateau (TP), precipitation-limited Mongolian Plateau (MP), and nutrient-limited Loess Plateau (LP)], we conducted a comparative survey of the east-west grassland transects on the three plateaus and explored the factors limiting regional productivity and their underlying mechanisms. The results showed that aboveground net primary productivity (ANPP) of LP (109.10 ± 16.76 g m-2 yr-1) was significantly higher than that of MP (66.71 ± 11.11 g m-2 yr-1) and TP (57.02 ± 10.59 g m-2 yr-1). The response rate of ANPP with environmental changes was different among different plateaus, being closely related to the main limiting factors. On MP, this was precipitation, on LP it was temperature and nutrients, and on TP, it was non-specific, reflecting restriction by the extremely low temperature. After autocorrelation screening of environmental factors, different regions exhibited different productivity response mechanisms. MP was mainly influenced by temperature and precipitation, LP was influenced by temperature and nutrient, and TP was influenced by nutrient, reflecting the modifying effect of the main limiting factors. The effect of each regional environment on ANPP was 72.56% on average and only 27.18% after simple regional integration. The regional model could optimize the simulation error of the integrated model, and the relative deviations in MP, LP, and TP were reduced by 31.76%, 17.22%, and 2.23%, respectively. These findings indicate that the grasslands on the three plateaus may have different or even the opposite mechanisms to control productivity.

18.
Molecules ; 25(20)2020 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-33066055

RESUMO

Esterases are a large family of enzymes with wide applications in the industry. However, all esterases originated from natural sources, limiting their use in harsh environments or newly- emerged reactions. In this study, we designed a new esterase to develop a new protocol to satisfy the needs for better biocatalysts. The ideal spatial conformation of the serine catalytic triad and the oxygen anion hole at the substrate-binding site was constructed by quantum mechanical calculation. The catalytic triad and oxygen anion holes were then embedded in the protein scaffold using the new enzyme protocol in Rosetta 3. The design results were subsequently evaluated, and optimized designs were used for expression and purification. The designed esterase had significant lytic activities towards p-nitrophenyl acetate, which was confirmed by point mutations. Thus, this study developed a new protocol to obtain novel enzymes that may be useful in unforgiving environments or novel reactions.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA