Catalytic mechanism of the tryptophan activation reaction revealed by crystal structures of human tryptophanyl-tRNA synthetase in different enzymatic states

Human tryptophanyl-tRNA synthetase (hTrpRS) differs from its bacterial counterpart at several key positions of the catalytic active site and has an extra N-terminal domain, implying possibly a different catalytic mechanism. We report here the crystal structures of hTrpRS in complexes with Trp, tryptophanamide and ATP and tryptophanyl-AMP, respectively, which represent three different enzymatic states of the Trp activation reaction. Analyses of these structures reveal the molecular basis of the mechanisms of the substrate recognition and the activation reaction. The dimeric hTrpRS is structurally and functionally asymmetric with half-of-the-sites reactivity. Recognition of Trp is by an induced-fit mechanism involving conformational change of the AIDQ motif that creates a perfect pocket for the binding and activation of Trp and causes coupled movements of the N-terminal and C-terminal domains. The KMSAS loop appears to have an inherent flexibility and the binding of ATP stabilizes it in a closed conformation that secures the position of ATP for catalysis. Our structural data indicate that the catalytic mechanism of the Trp activation reaction by hTrpRS involves more moderate conformational changes of the structural elements at the active site to recognize and bind the substrates, which is more complex and fine-tuned than that of bacterial TrpRS

Low-firing and temperature stable microwave dielectric ceramics: Ba2LnV3O11 (Ln = Nd, Sm)

Low-firing and temperature stable microwave dielectric ceramics of Ba2LnV3O11 (Ln = Nd, Sm) were prepared by solid-state reaction. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the phase purity, crystal structure, sintering behavior, and microstructure. The XRD patterns indicated that Ba2LnV3O11 (Ln =Nd, Sm) ceramics belong to monoclinic crystal system with P21/c space group in the whole sintering temperature range (800-900 °C). Both ceramics could be well densified at 880 °C for 4 h with relative densities higher than 96%. The Ba2LnV3O11 (Ln =Nd, Sm) samples sintered at 880 °C for 4 h exhibited excellent microwave dielectric properties: εr = 12.05, Q×f = 23,010 GHz, τf = –7.7 ppm/oC, and εr = 12.19, Q×f = 27,120 GHz, τf = –16.2 ppm/oC, respectively. Besides, Ba2LnV3O11 (Ln =Nd, Sm) ceramics could be well co-fired with the silver electrode at 880 °C

Brain relaxation using desflurane anesthesia and total intravenous anesthesia in patients undergoing craniotomy for supratentorial tumors: a randomized controlled study

Abstract Background Satisfactory brain relaxation is essential in neurosurgery. Desflurane anesthesia and propofol-based total intravenous anesthesia (TIVA) have different effects on cerebral hemodynamics, potentially contributing to discrepant brain relaxation. The purpose of this study was to compare the effects of desflurane and TIVA on brain relaxation in patients undergoing craniotomy for supratentorial tumors. Methods In this randomized, controlled study, we enrolled patients aged 18–60 years, with ASA I–III, who were scheduled to undergo elective craniotomy for supratentorial tumors. Patients were randomly assigned in a 1:1 ratio to receive desflurane anesthesia or TIVA. The primary outcome was the proportion of satisfactory brain relaxation. Secondary outcomes included emergence and extubation times, recovery of cognitive function and postoperative complications. Results Of 369 patients who were assessed for eligibility, 111 were randomized and 110 were included in the modified intention-to-treat analysis (55 in the desflurane group and 55 in the TIVA group). The proportion of satisfactory brain relaxation was similar between the two groups: 69% in the desflurane group and 73% in the TIVA group (RR: 0.950, 95% CI: 0.748–1.207; P = 0.675). Patients assigned to the desflurane group had shorter emergence (10 [8–13] min vs. 13 [10–20] min, P < 0.001) and extubation times (13 [10–18] min vs. 17 [13–23] min, P < 0.001), and better recovery of cognitive function at 15 min after extubation (16 [0–24] vs. 0 [0–20], P = 0.003), but experienced increased postoperative nausea and vomiting (PONV) (16 [29%] vs. 6 [11%] P = 0.017) and tachycardia (22 [40%] vs. 9 [16%], P = 0.006) during recovery. Conclusions Desflurane anesthesia and TIVA provide similar brain relaxation in patients without intracranial hypertension undergoing elective craniotomy. Desflurane accelerates the recovery from anesthesia but is associated with increased PONV and tachycardia during the recovery period. Trial registration Clinicaltrial.gov (NCT04691128). Date of registration: December 31, 2020

Discovery of Acupoints and Combinations with Potential to Treat Vascular Dementia: A Data Mining Analysis

The prevalence of vascular dementia (VaD) is high among the elderly. Acupuncture, a popular therapeutic method in China, can improve memory, orientation, calculation, and self-managing ability in VaD patients. However, in clinical acupuncture and acupuncture research, the selection of acupoints to treat VaD remains challenging. This study aimed to discover acupoints and acupoint combinations with potential for VaD based on data mining. After database searching and screening for articles on clinical trials evaluating the effects of acupuncture on VaD, 238 acupuncture prescriptions were included for further analysis. Baihui (GV 20), Sishencong (EX-HN 1), Fengchi (GB 20), Shuigou (GV 26), and Shenting (GV 24) appeared most frequently in the modern literature and are potential acupoints for VaD. Combinations between Baihui (GV 20), Sishencong (EX-HN 1), Fengchi (GB 20), Shenting (GV 24), Shuigou (GV 26), and Zusanli (ST 36) were most frequent and represent potential combinations for VaD treatment. These results provide a reference for the selection and combination of acupoints to treat VaD in clinical acupuncture and acupuncture research

Effect of intraoperative muscle relaxation reversal on the success rate of motor evoked potential recording in patients undergoing spinal surgery: a randomized controlled trial

Abstract Background Partial neuromuscular blockade (NMB) has been applied for some surgeries to reduce bleeding and prevent patient movement for spinal surgery. Sugammadex selectively binds to rocuronium in the plasma and consequently lowers the rocuronium concentration at the neuromuscular junction. In this study, we aimed to observe whether the success rate of transcranial motor-evoked potential (TceMEP) can be increased by sugammadex compared with partial NMB during spinal surgery. Methods Patients who underwent elective spinal surgery with TceMEP monitoring were randomly assigned to the sugammadex group and control group. Rocuronium was continuously infused to maintain the train of four counts (TOFc) = 2. The sugammadex group discontinued rocuronium infusion at the time of TceMEP monitoring and was infused with 2 mg/kg sugammadex; the control group was infused with the same dose of saline. Results A total of 171 patients were included. The success rate of TceMEP monitoring in the sugammadex group was significantly higher than that in the control group. TceMEP amplitudes were greater in the sugammadex group than in the control group at 5 min, 10 min, and 20 min after the start of motor-evoked potential monitoring. The latencies of upper extremity TceMEPs monitoring showed no difference between groups. TOF ratios were greater in the sugammadex group at 5 min, 10 min, and 20 min after the start of motor-evoked potential monitoring. There were no adverse effects caused by sugammadex. Conclusions Sugammadex can improve the success rate of motor-evoked potential monitoring compared with moderate neuromuscular blockade induced by continuous infusion of rocuronium in spinal surgery. Trial registration The study was registered on clinicaltrials.gov.cn on 29/10/2020 (trial registration number: NCT04608682)

Structural, infrared reflectivity spectra and microwave dielectric properties of the Li₇Ti₃O₉F ceramic

Abstract A cubic rock salt structured ceramic, Li₇Ti₃O₉F, was fabricated via the conventional solid-state reaction route. The synthesis conditions, sintering characteristics, and microwave dielectric properties of Li₇Ti₃O₉F ceramics were investigated by X-ray diffraction (XRD), thermal dilatometer, Scanning Electron Microscopy (SEM) accompanied with EDS mapping, and microwave resonant measurements. Rietveld refinement, selected area electron diffraction (SAED) pattern and high-resolution transmission electron microscopy (HRTEM) confirmed that Li₇Ti₃O₉F adopts a cubic rock-salt structure. The ceramic sintered at 950 °C presented the optimal microwave properties of εᵣ = 22.5, Q×f = 88,200 GHz, and τf  = −24.2 ppm/°C. Moreover, good chemical compatibility with Ag was verified through cofiring at 950 °C for 2 h. These results confirm a large potential for Li₇Ti₃O₉F ceramic to be utilized as substrates in the low temperature cofired ceramic (LTCC) technology. This work provides the possibility to exploit low-temperature-firing ceramics through solid solution between oxides and fluorides

Molecular docking and molecular dynamics simulations reveal the clinical resistance of the gatekeeper mutation V564F of FGFR2 against Infigratinib

AbstractFibroblast growth factor receptor 2 (FGFR2), as a transmembrane receptor tyrosine kinase, is implicated in a plethora of human cancers, including intrahepatic cholangiocarcinomas, breast cancers, and non-small cell lung cancer. The clinically relevant V564F gatekeeper mutation conferred resistance to current FGFR2 drug − Infigratinib. In this study, the protein − ligand interactions between FGFR2 kinase domain (wild-type and V564F) and Infigratinib were compared through an integrated computational method. The multiple, large-scale molecular dynamics (MD) simulations, together with dynamic cross-correlation analysis and binding free energy calculations suggested that the resistant mutation may not trigger the conformational changes of the FGFR2 kinase domain. The simulation results also indicated that the driving force to decrease the binding affinity of Infigratinib to the FGFR2 V564F variant derived from the difference in the protein − ligand hydrogen bonding interactions. Moreover, the per-residue free energy decomposition analysis revealed that the reduced contributions from several residues in the ATP-binding site of FGFR2, especially Glu565 and Ala567 located at the kinase hinge domain, were the key residues responsible for the loss of binding affinity of Infigratinib to the V564F variant. This study may offer useful information for the design of novel selective kinase inhibitors targeting FGFR2

Targeted delivery of microRNA 146b mimic to hepatocytes by lactosylated PDMAEMA nanoparticles for the treatment of NAFLD

<p>Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide, and precision therapeutic will be a benefit for the NAFLD regression. In this study, we observed low microRNA 146 b (miR-146 b) expression in NAFLD mice model induced by methionine–choline-deficient diet (MCD) compared with control group. Furthermore, miR-146b^−/− mice induced MCD exhibited severe liver steatosis and hepatitis. A bio-distribution study showed that novel Lactosylated PDMAEMA nanoparticles effectively targeted hepatocytes Lac-PDMAEMA. We coupled miR-146b mimic with Lac-PDMAEMA and then were administrated to NAFLD mice model, which could obviously alleviate the hepatic steatosis. Lac-PDMAEMA effectively delivered miR-146b mimic to hepatocytes with a ∼8-fold upregulation of miR-146b mimic targeting MyD88 and IRAK1, and in turn suppressed the expression of PPARγ. Meanwhile, TNF-α and IL-6 mRNA levels were decreased after administration of Lac-PDMAEMA/miR-146b mimic. So, we made a conclusion that targeted delivering miR-146b mimic to the hepatocytes by, coupling Lac-PDMAEMA nanoparticles could effectively alleviate the hepatic steatosis in NAFLD mice, which maybe bring a new and effective way to intervene and therapy the NAFLD.</p

Hypoxic Preconditioning with Cobalt of Bone Marrow Mesenchymal Stem Cells Improves Cell Migration and Enhances Therapy for Treatment of Ischemic Acute Kidney Injury

<div><p>Mesenchymal stem cell (MSC) administration is known to enhance the recovery of the kidney following injury. Here we tested the potential of hypoxic-preconditioned-MSC transplantation to enhance the efficacy of cell therapy on acute kidney injury (AKI) by improving MSC migration to the injured kidney. Cobalt was used as hypoxia mimetic preconditioning (HMP). MSC were subjected to HMP through 24 h culture in 200 µmol/L cobalt. Compared to normoxia cultured MSC (NP-MSC), HMP significantly increased the expression of HIF-1α and CXCR4 in MSC and enhanced the migration of MSC <i>in vitro</i>. This effect was lost when MSC were treated with siRNA targeting HIF-1α or CXCR4 antagonist. SPIO labeled MSC were administered to rats with I/R injury followed immediately by magnetic resonance imaging. Imaging clearly showed that HMP-MSC exhibited greater migration and a longer retention time in the ischemic kidney than NP-MSC. Histological evaluation showed more HMP-MSC in the glomerular capillaries of ischemic kidneys than in the kidneys receiving NP-MSC. Occasional tubules showed iron labeling in the HMP group, while no tubules had iron labeling in NP group, indicating the possibility of tubular transdifferentiation after HMP. These results were also confirmed by fluorescence microscopy study using CM-DiI labeling. The increased recruitment of HMP-MSC was associated with reduced kidney injury and enhanced functional recovery. This effect was also related to the increased paracrine action by HMP-MSC. Thus we suggest that by enhancing MSC migration and prolonging kidney retention, hypoxic preconditioning of MSC may be a useful approach for developing AKI cell therapy.</p></div