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1.
Front Psychol ; 12: 731850, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34744902

RESUMO

In China, the mature development of online retail channels provides consumers with multiple consumption choices, and the factors that affect whether consumers choose to search or purchase online are numerous and complex. In this context, this paper reports on experimental research regarding consumers' willingness to choose channels based on the two-stage decision-making theory. Using structural equation modeling, the factors influencing consumers' online search intention and purchase willingness and the relationship between them are studied. In particular, the perceived benefits, channel trust, and channel transfer costs are explored. Furthermore, a Bayesian network is used in order to analyze the degree of influence of each factor quantitatively. It is found that online trust is an important factor affecting consumers' online search intention, and the most important factor for consumers' online purchase intention is their perceived benefits of online shopping. At the same time, there is a positive relationship between online search intention and purchase intention. This study can provide management decision support for online retail enterprises and help to promote the healthy development of online shopping.

2.
Int J Ophthalmol ; 14(11): 1741-1747, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34804865

RESUMO

AIM: To explore the intrinsic brain activity variations in retinal vein occlusion (RVO) subjects by using the voxel-wise degree centrality (DC) technique. METHODS: Twenty-one subjects with RVO and twenty-one healthy controls (HCs) were enlisted and underwent the resting-state functional magnetic resonance imaging (rs-fMRI) examination. The spontaneous cerebrum activity variations were inspected using the DC technology. The receiver operating characteristic (ROC) curve was implemented to distinguish the DC values of RVOs from HCs. The relationships between DC signal of definite regions of interest and the clinical characteristics in RVO group were evaluated by Pearson's correlation analysis. RESULTS: RVOs showed notably higher DC signals in right superior parietal lobule, middle frontal gyrus and left precuneus, but decreased DC signals in left middle temporal gyrus and bilateral anterior cingulated (BAC) when comparing with HCs. The mean DC value of RVOs in the BAC were negatively correlated with the anxiety and depression scale. CONCLUSION: RVO is associated aberrant intrinsic brain activity patterns in several brain areas including pain-related as well as visual-related regions, which might assist to reveal the latent neural mechanisms.

3.
Front Neurosci ; 15: 718973, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34720858

RESUMO

Background: Using resting-state functional connectivity (rsFC), we investigated alternations in spontaneous brain activities reflected by functional connectivity density (FCD) in patients with optic neuritis (ON). Methods: We enrolled 28 patients with ON (18 males, 10 females) and 24 healthy controls (HCs; 16 males, 8 females). All subjects underwent functional magnetic resonance imaging (fMRI) in a quiet state to determine the values of rsFC, long-range FCD (longFCD), and short-range FCD (IFCD). Receiver operating characteristic (ROC) curves were generated to distinguish patients from HCs. Results: The ON group exhibited obviously lower longFCD values in the left inferior frontal gyrus triangle, the right precuneus and the right anterior cingulate, and paracingulate gyri/median cingulate and paracingulate gyri. The left median cingulate and paracingulate gyri and supplementary motor area (SMA) were also significantly lower. Obviously reduced IFCD values were observed in the left middle temporal gyrus/angular gyrus/SMA and right cuneus/SMA compared with HCs. Conclusion: Abnormal neural activities were found in specific brain regions in patients with ON. Specifically, they showed significant changes in rsFC, longFCD, and IFCD values. These may be useful to identify the specific mechanism of change in brain function in ON.

4.
Front Cardiovasc Med ; 8: 670594, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34595214

RESUMO

Purpose: To detect lung metastases, we conducted a retrospective study to improve patient prognosis. Methods: Hypertension patients with ocular metastases (OM group; n = 58) and without metastases (NM group; n = 1,217) were selected from individuals with lung cancer admitted to our hospital from April 2005 to October 2019. The clinical characteristics were compared by Student's t-test and chi-square test. Independent risk factors were identified by binary logistic regression, and their diagnostic value evaluated by receiver operating characteristic curve analysis. Results: Age and sex did not differ significantly between OM and NM groups; There were significant differences in pathological type and treatment. Adenocarcinoma was the main pathological type in the OM group (67.24%), while squamous cell carcinoma was the largest proportion (46.43%) in the NM group, followed by adenocarcinoma (34.10%). The OM group were treated with chemotherapy (55.17%), while the NM group received both chemotherapy (39.93%) and surgical treatment (37.06%). Significant differences were detected in the concentrations of cancer antigen (CA)-125, CA-199, CA-153, alpha fetoprotein (AFP), carcinoembryonic antigen (CEA), cytokeratin fraction 21-1 (CYFRA21-1), total prostate-specific antigen, alkaline phosphatase, and hemoglobin (Student's t-test). Binary logistic regression analysis indicated that CA-199, CA-153, AFP, CEA, and CYRFA21-1 were independent risk factors for lung cancer metastasis. AFP (98.3%) and CEA (89.3%) exhibited the highest sensitivity and specificity, respectively, while CYRFA21-1 had the highest area under the ROC curve value (0.875), with sensitivity and specificity values of 77.6 and 87.0%, respectively. Hence, CYFRA21-1 had the best diagnostic value.

5.
Cancer Discov ; 2021 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-34642171

RESUMO

Gastric cancer (GC) heterogeneity represents a barrier to disease management. We generated a comprehensive single-cell atlas of GC (>200,000 cells) comprising 48 samples from 31 patients across clinical stages and histological subtypes. We identified 34 distinct cell-lineage states including novel rare cell populations. Many lineage states exhibited distinct cancer-associated expression profiles, individually contributing to a combined tumor-wide molecular collage. We observed increased plasma cell proportions in diffuse-type tumors associated with epithelial-resident KLF2, and stage-wise accrual of cancer-associated fibroblast sub-populations marked by high INHBA and FAP co-expression. Single-cell comparisons between patient-derived organoids (PDOs) and primary tumors highlighted inter- and intra-lineage similarities and differences, demarcating molecular boundaries of PDOs as experimental models. We complemented these findings by spatial transcriptomics, orthogonal validation in independent bulk RNA-seq cohorts, and functional demonstration using in vitro and in vivo models. Our results provide a high-resolution molecular resource of intra- and inter-patient lineage-states across distinct GC subtypes.

6.
Nat Commun ; 12(1): 5979, 2021 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-34645801

RESUMO

The lobula giant movement detector (LGMD) is the movement-sensitive, wide-field visual neuron positioned in the third visual neuropile of lobula. LGMD neuron can anticipate collision and trigger avoidance efficiently owing to the earlier occurring firing peak before collision. Vision chips inspired by the LGMD have been successfully implemented in very-large-scale-integration (VLSI) system. However, transistor-based chips and single devices to simulate LGMD neurons make them bulky, energy-inefficient and complicated. The devices with relatively compact structure and simple operation mode to mimic the escape response of LGMD neuron have not been realized yet. Here, the artificial LGMD visual neuron is implemented using light-mediated threshold switching memristor. The non-monotonic response to light flow field originated from the formation and break of Ag conductive filaments is analogue to the escape response of LGMD neuron. Furthermore, robot navigation with obstacle avoidance capability and biomimetic compound eyes with wide field-of-view (FoV) detection capability are demonstrated.

7.
Front Psychiatry ; 12: 706443, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34707517

RESUMO

Background: The coronavirus infection disease 2019 (COVID-19) pandemic is likely to put healthcare professionals across the world in an unprecedented situation. Methods: A total of 683 healthcare workers were recruited in this study. Short form-12 items (SF-12), Societal Influences Survey Questionnaire (SISQ), and Disaster-Related Psychological Screening Test (DRPST) were used to survey participants. Multiple linear regression and structural equation model (SEM) were used to explore the possible factors to the societal influences and quality of life. Results: After multiple linear regression analysis, female, older, more education years, married, regular intake, and posttraumatic stress disorder (PTSD) frequency had positive association with SISQ. To physical component summary (PCS) of SF-12, chronic illness, sleep score, PTSD frequency, and social distance had negative association, and exercise habits had positive association. A mental component summary (MCS) value of SF-12, age, participate in social activities, and social information had positive association, and PTSD frequency, sleep score, social anxiety, and depression had negative association. Under SEM analysis, PTSD had positive influence on SISQ. Sleep score and MCS value had negative influences on SISQ. PTSD severity, older age, sleep score, smoking, and nursing staff had negative influences on PCS value. Young age, PTSD frequency, sleep score, and depression had negative influences on MCS value. Conclusion: Healthcare team members with severe PTSD symptoms suffered more societal influences. Relative to PTSD severity, PTSD frequency was more important to the quality of life. Members of older age who frequently participate in clubs, volunteers, or charity activities had better mental life quality.

8.
Children (Basel) ; 8(9)2021 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-34572164

RESUMO

Advanced neonatal care has increased the survival of neonates born prematurely, and prematurity is a well-known risk factor for asthma/wheezing disorders. Thus, this prospective study aimed to determine the early life factors associated with preschool wheezing in premature neonates. Preterm neonates born between 2012 and 2017 were recruited, excluding those with bacterial infection within 7 days of life, maternal sepsis, and maternal chorioamnionitis. Birth and admission history, comorbidities, and maternal history were documented. Respiratory problems were followed-up at the neonatal outpatient department. Patients were divided into wheezing and non-wheezing groups. Data were analyzed using the Mann-Whitney test and Fisher's exact test, and multivariable logistic regression was used to define the risk factors of preschool wheezing/asthma. A total of 125 preterm infants were enrolled, including 19 in the wheezing group and 106 in the non-wheezing group. Patients in the wheezing group had longer duration of intubation (p = 0.025), higher rates for exclusive breast milk feeding (p = 0.012), and higher re-hospitalization rates for respiratory tract infections (p < 0.001), especially for respiratory syncytial virus (RSV) bronchiolitis (p = 0.045). The incidence of allergic rhinitis was also higher in the wheezing group (p = 0.005). After multivariable logistic regression, allergic rhinitis and re-hospitalization for respiratory tract infections were two significant risk factors for preschool wheezing/asthma in premature neonates. Close follow-up of premature infants at high risk for asthma susceptibility is recommended.

9.
Front Genet ; 12: 702695, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34589114

RESUMO

MicroRNAs (miRNAs) are approximately 20-22 nucleotides in length, which are well known to participate in the post-transcriptional modification. The mature miRNAs were observed to be varied on 5' or 3' that raise another term-the isoforms of mature miRNAs (isomiRs), which have been proven not the artifacts and discussed widely recently. In our research, we focused on studying the 5' isomiRs in lung adenocarcinoma (LUAD) in The Cancer Genome Atlas (TCGA). We characterized 75 isomiRs significantly associated with better prognosis and 43 isomiRs with poor prognosis. The 75 protective isomiRs can successfully distinguish tumors from normal samples and are expressed differently between patients of early and late stages. We also found that most of the protective isomiRs tend to be with downstream shift and upregulated compared with those with upstream shift, implying that a possible selection occurs during cancer development. Among these protective isomiRs, we observed a highly positive and significant correlation, as well as in harmful isomiRs, suggesting cooperation within the group. However, between protective and harmful, there is no such a concordance but conversely more negative correlation, suggesting the possible antagonistic effect between protective and harmful isomiRs. We also identified that two isomiRs miR-181a-3p|-3 and miR-181a-3p|2, respectively, belong to the harmful and protective groups, suggesting a bidirectional regulation of their originated archetype-miR-181a-3p. Additionally, we found that the protective isomiRs of miR-21-5p, which is an oncomiR, may be evolved as the tumor suppressors through producing isomiRs to hinder metastasis. In summary, these results displayed the characteristics of the protective isomiRs and their potential for developing the treatment of lung cancer.

10.
Front Oncol ; 11: 680303, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34513671

RESUMO

Background: In this study, we designed a new (Su'S) target area delineation to protect the normal liver during liver regeneration and prospectively evaluate liver regeneration after radiotherapy, as well as to explore the clinical factors of liver regeneration and established a model and nomogram. Methods: Thirty patients treated with preoperative downstaging radiotherapy were prospectively included in the training cohort, and 21 patients treated with postoperative adjuvant radiotherapy were included in the validation cohort. The cut-off points of each optimal predictor were obtained using receiver-operating characteristic analysis. A model and nomogram for liver regeneration after radiotherapy were developed and validated. Results: After radiotherapy, 12 (40%) and 13 (61.9%) patients in the training and validation cohorts experienced liver regeneration, respectively. The risk stratification model based on the cutoffs of standard residual liver volume spared from at least 20 Gy (SVs20 = 303.4 mL/m2) and alanine aminotransferase (ALT=43 u/L) was able to effectively discriminate the probability of liver regeneration. The model and nomogram of liver regeneration based on SVs20 and ALT showed good prediction performance (AUC=0.759) in the training cohort and performed well (AUC=0.808) in the validation cohort. Conclusions: SVs20 and ALT were optimal predictors of liver regeneration. This model may be beneficial to the constraints of the normal liver outside the radiotherapy-targeted areas.

11.
Front Plant Sci ; 12: 696698, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34490001

RESUMO

Fructose-1,6-biphosphate aldolase (FBA) is a multifunctional enzyme in plants, which participates in the process of Calvin-Benson cycle, glycolysis and gluconeogenesis. Despite the importance of FBA genes in regulating plant growth, development and abiotic stress responses, little is known about their roles in cotton. In the present study, we performed a genome-wide identification and characterization of FBAs in Gossypium hirsutum. Totally seventeen GhFBA genes were identified. According to the analysis of functional domain, phylogenetic relationship, and gene structure, GhFBA genes were classified into two subgroups. Furthermore, nine GhFBAs were predicted to be in chloroplast and eight were located in cytoplasm. Moreover, the promoter prediction showed a variety of abiotic stresses and phytohormone related cis-acting elements exist in the 2k up-stream region of GhFBA. And the evolutionary characteristics of cotton FBA genes were clearly presented by synteny analysis. Moreover, the results of transcriptome and qRT-PCR analysis showed that the expression of GhFBAs were related to the tissue distribution, and further analysis suggested that GhFBAs could respond to various abiotic stress and phytohormonal treatments. Overall, our systematic analysis of GhFBA genes would not only provide a basis for the understanding of the evolution of GhFBAs, but also found a foundation for the further function analysis of GhFBAs to improve cotton yield and environmental adaptability.

12.
J Environ Manage ; 300: 113700, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34517231

RESUMO

Electroplating sludge is a hazardous waste produced in large quantities in the electroplating industry during production. It is rich in heavy metal resources and can be recovered as value-added heavy metal products. To recover Zn in electroplating sludge, Fe/Al/Ca impurities were effectively removed as hematite, boehmite, and calcium sulfate, respectively, via a facile hydrothermal method with reduction of nitric acid by addition of glucose. After the sludge was dissolved in nitric acid, the generated solution contained 6.1 g/L of Zn, 2.2 g/L of Fe, 2.5 g/L of Al, and 2.9 g/L of Ca. First, approximately 100% Fe was extracted as hematite nanoparticles containing 94.6 wt% Fe2O3 after the solution was treated at 190 °C for 6 h. Second, when the temperature was elevated to 270 °C, nearly 99% Al was isolated as boehmite particles containing 95.2 wt% Al2O3. Third, more than 98% Ca was removed as anhydrite, which contained 95.9 wt% CaSO4, by adding sulfuric acid. During the steps, the total loss of Zn was less than 3%, and 5.75 g/L of residual Zn was recovered as zincite containing 92.2 wt% ZnO by adjusting the pH to 8. The dissolved Fe, Al, and Ca impurities were successfully removed as purified hematite, boehmite, and anhydrite, respectively, through the stepwise separation method by adjusting reaction temperatures and pH. The high content of Zn in the electroplating sludge was finally purified as zincite.


Assuntos
Metais Pesados , Esgotos , Galvanoplastia , Reciclagem , Zinco
13.
Small ; 17(41): e2103175, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34528382

RESUMO

The mimicking of both homosynaptic and heterosynaptic plasticity using a high-performance synaptic device is important for developing human-brain-like neuromorphic computing systems to overcome the ever-increasing challenges caused by the conventional von Neumann architecture. However, the commonly used synaptic devices (e.g., memristors and transistors) require an extra modulate terminal to mimic heterosynaptic plasticity, and their capability of synaptic plasticity simulation is limited by the low weight adjustability. In this study, a WSe2 -based memtransistor for mimicking both homosynaptic and heterosynaptic plasticity is fabricated. By applying spikes on either the drain or gate terminal, the memtransistor can mimic common homosynaptic plasticity, including spiking rate dependent plasticity, paired pulse facilitation/depression, synaptic potentiation/depression, and filtering. Benefitting from the multi-terminal input and high adjustability, the resistance state number and linearity of the memtransistor can be improved by optimizing the conditions of the two inputs. Moreover, the device can successfully mimic heterosynaptic plasticity without introducing an extra terminal and can simultaneously offer versatile reconfigurability of excitatory and inhibitory plasticity. These highly adjustable and reconfigurable characteristics offer memtransistors more freedom of choice for tuning synaptic weight, optimizing circuit design, and building artificial neuromorphic computing systems.


Assuntos
Plasticidade Neuronal , Sinapses , Humanos
14.
Histol Histopathol ; : 18375, 2021 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-34528700

RESUMO

AIMS: The present study aims to determine the expression of interleukin (IL)-10 in peripheral blood of patients with sepsis, and investigate its effects on the biological function of vascular endothelial cells. METHODS: Thirty-six sepsis patients and 20 healthy subjects were included. Peripheral blood was collected from all subjects. ELISA was used to determine IL-10 content in serum. A ratio of IL-10+ T cells was determined by flow cytometry. CCK-8 assay was used to investigate proliferation. Cell cycle and apoptosis were analyzed by flow cytometry. Western blotting was used to examine the expression of phosphorylated STAT3 protein. RESULTS: The content of IL-10 and the ratio of IL-10+ T cells were enhanced in pa-tients with sepsis. Serum from patients with sepsis inhibited the proliferation of HU-VECs, and addition of IL-10 antibody reversed this effect. IL-10 in the serum from patients with sepsis promoted the apoptosis of HUVECs. IL-10 inhibited the proliferation and promoted the apoptosis of HUVECs by enhancing the phosphorylation of STAT3. CONCLUSIONS: The present study demonstrates that the content of IL-10 and the ratio of IL-10+ T cells in peripheral blood of patients with sepsis are up-regulated, and this inhibits HUVEC proliferation and promotes HUVEC apoptosis through STAT3 sig-naling pathway. The results in this study provide a new experimental basis for further understanding the molecular mechanism of sepsis-induced vascular injury.

15.
J Matern Fetal Neonatal Med ; : 1-3, 2021 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-34496712

RESUMO

OBJECTIVE: To assess the efficacy of positive feedback closed-loop management system (PFCMS) protocol in influencing parents' decision about pregnancy continuation in pregnancies diagnosed with omphalocele. METHODS: This was a retrospective cohort study of patients who were diagnosed with fetal omphalocele prior to 20 weeks' gestation by ultrasound and were referred to Fetal Care Center at a mainland Chinese medical center during an 11-year period. Two management strategies were offered during the two stages of the study period: a single consultant with a routine protocol and a multidisciplinary support team with PFCMS, respectively. We analyzed the two protocols influencing parents' decision about pregnancy continuation. RESULTS: Forty-nine patients diagnosed with fetal omphalocele were included in this study. In Group A including 16 patients with routine protocol during the first stage of the study period, the majority opted for termination, and only five continued the pregnancy. In Group B including 33 patients with PFCMS during the second stage of the study period, less than one third chose TOP, and 23 ended in live births. There was a significantly lower TOP rate in patients treated with the PFCMS protocol. CONCLUSION: The PFCMS protocol may be an efficient approach in managing pregnancies complicated by omphalocele, which may help in preventing unnecessary pregnancy terminations.

16.
Artigo em Inglês | MEDLINE | ID: mdl-34468890

RESUMO

PURPOSE: The relationship between height and incident atrial fibrillation (AF) has recently been demonstrated. We aimed to evaluate the impact of height on outcomes of ablation in patients with drug-refractory symptomatic paroxysmal AF (PAF). METHODS: A total of 689 patients (470 males; age, 53.0 ± 11.7 years) with symptomatic paroxysmal AF receiving index catheter ablation (CA) between 2003 and 2013 were enrolled in this study. The baseline characteristics, ablation, and follow-up results were evaluated. The patients were categorized according to the quartiles of height for each sex. RESULTS: Patients in the lower quartiles of height had a lower incidence of AF recurrence (log-rank p = 0.022). Height in female patients was strongly associated with AF recurrence (p = 0.027) after an index ablation in the 6.33 ± 4.32 years of follow-up. Female patients > 159 cm in height had a higher likelihood of AF recurrence after index CA (HR = 2.01, 95% CI: 1.24-3.25, p = 0.005) than that in those below this height. In computed tomography (CT) scan, the superoinferior diameter of the left atrium (LA) correlated with body height in females, but not in male patients. CONCLUSIONS: Height is associated with AF recurrence after the index CA of PAF in female patients. In Asian populations, women above height 159 cm are twice as likely to have AF recurrence post-ablation as shorter women.

17.
ACS Appl Mater Interfaces ; 13(33): 39595-39605, 2021 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-34378376

RESUMO

Two-dimensional MXene has enormous potential for application in industry and academia owing to its surface hydrophilicity and excellent electrochemical properties. However, the application of MXene in optoelectronic memory and logical computing is still facing challenges. In this study, an optoelectronic resistive random access memory (RRAM) based on silver nanoparticles (Ag NPs)@MXene-TiO2 nanosheets (AMT) was prepared through a low-cost and facile hydrothermal oxidation process. The fabricated device exhibited a typical bipolar switching behavior and controllable SET voltage. Furthermore, we successfully demonstrated a 4-bit in-memory digital comparator with AMT RRAMs, which can replace five logic gates in a traditional approach. The AMT-based digital comparator may open the door for future integrated functions and applications in optoelectronic data storage and simplify the complex logic operations.

19.
Nat Ecol Evol ; 5(10): 1338-1349, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34400825

RESUMO

Despite substantial conservation efforts, the loss of ecosystems continues globally, along with related declines in species and nature's contributions to people. An effective ecosystem goal, supported by clear milestones, targets and indicators, is urgently needed for the post-2020 global biodiversity framework and beyond to support biodiversity conservation, the UN Sustainable Development Goals and efforts to abate climate change. Here, we describe the scientific foundations for an ecosystem goal and milestones, founded on a theory of change, and review available indicators to measure progress. An ecosystem goal should include three core components: area, integrity and risk of collapse. Targets-the actions that are necessary for the goals to be met-should address the pathways to ecosystem loss and recovery, including safeguarding remnants of threatened ecosystems, restoring their area and integrity to reduce risk of collapse and retaining intact areas. Multiple indicators are needed to capture the different dimensions of ecosystem area, integrity and risk of collapse across all ecosystem types, and should be selected for their fitness for purpose and relevance to goal components. Science-based goals, supported by well-formulated action targets and fit-for-purpose indicators, will provide the best foundation for reversing biodiversity loss and sustaining human well-being.


Assuntos
Ecossistema , Objetivos , Biodiversidade , Mudança Climática , Conservação dos Recursos Naturais , Humanos
20.
Nucleic Acids Res ; 49(16): 9539-9547, 2021 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-34403461

RESUMO

In Escherichia coli, elevated levels of free l-tryptophan (l-Trp) promote translational arrest of the TnaC peptide by inhibiting its termination. However, the mechanism by which translation-termination by the UGA-specific decoding release factor 2 (RF2) is inhibited at the UGA stop codon of stalled TnaC-ribosome-nascent chain complexes has so far been ambiguous. This study presents cryo-EM structures for ribosomes stalled by TnaC in the absence and presence of RF2 at average resolutions of 2.9 and 3.5 Å, respectively. Stalled TnaC assumes a distinct conformation composed of two small α-helices that act together with residues in the peptide exit tunnel (PET) to coordinate a single L-Trp molecule. In addition, while the peptidyl-transferase center (PTC) is locked in a conformation that allows RF2 to adopt its canonical position in the ribosome, it prevents the conserved and catalytically essential GGQ motif of RF2 from adopting its active conformation in the PTC. This explains how translation of the TnaC peptide effectively allows the ribosome to function as a L-Trp-specific small-molecule sensor that regulates the tnaCAB operon.


Assuntos
Proteínas de Escherichia coli/ultraestrutura , Fatores de Terminação de Peptídeos/ultraestrutura , Biossíntese de Proteínas , Ribossomos/ultraestrutura , Códon de Terminação/genética , Microscopia Crioeletrônica , Escherichia coli/genética , Escherichia coli/ultraestrutura , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Fatores de Terminação de Peptídeos/química , Fatores de Terminação de Peptídeos/genética , Conformação Proteica , Conformação Proteica em alfa-Hélice , Ribossomos/genética , Triptofano/genética
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