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1.
Nat Immunol ; 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31611699

RESUMO

Self-non-self discrimination is central to T cell-mediated immunity. The kinetic proofreading model can explain T cell antigen receptor (TCR) ligand discrimination; however, the rate-limiting steps have not been identified. Here, we show that tyrosine phosphorylation of the T cell adapter protein LAT at position Y132 is a critical kinetic bottleneck for ligand discrimination. LAT phosphorylation at Y132, mediated by the kinase ZAP-70, leads to the recruitment and activation of phospholipase C-γ1 (PLC-γ1), an important effector molecule for T cell activation. The slow phosphorylation of Y132, relative to other phosphosites on LAT, is governed by a preceding glycine residue (G131) but can be accelerated by substituting this glycine with aspartate or glutamate. Acceleration of Y132 phosphorylation increases the speed and magnitude of PLC-γ1 activation and enhances T cell sensitivity to weaker stimuli, including weak agonists and self-peptides. These observations suggest that the slow phosphorylation of Y132 acts as a proofreading step to facilitate T cell ligand discrimination.

2.
Int J Nanomedicine ; 14: 7879-7889, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31576129

RESUMO

Introduction and objective: Precisely and sensitively diagnosing diseases especially early and accurate tumor diagnosis in clinical magnetic resonance (MR) scanner is a highly demanding but challenging task. Gadolinium (Gd) chelate is the most common T 1 magnetic resonance imaging (MRI) contrast agent at present. However, traditional Gd-chelates are suffering from low relaxivity, which hampers its application in clinical diagnosis. Currently, the development of nano-sized Gd based T 1 contrast agent, such as incorporating gadolinium chelate into nanocarriers, is an attractive and feasible strategy to enhance the T 1 contrast capacity of Gd chelate. The objective of this study is to improve the T 1 contrast ability of Gd-chelate by synthesizing nanoparticles (NPs) for accurate and early diagnosis in clinical diseases. Methods: Reverse microemulsion method was used to coat iron oxide (IO) with tunable silica shell and form cores of NPs IO@SiO2 at step one, then Gd-chelate was loaded on the surface of silica-coated iron oxide NPs. Finally, Gd-based silica coating magnetite NPs IO@SiO2-DTPA-Gd was developed and tested the ability to detect tumor cells on the cellular and in vivo level. Results: The r 1 value of IO@SiO2-DTPA-Gd NPs with the silica shell thickness of 12 nm was about 33.6 mM-1s-1, which was approximately 6 times higher than Gd-DTPA, and based on its high T 1 contrast ability, IO@SiO2-DTPA-Gd NPs could effectively detect tumor cells on the cellular and in vivo level. Conclusion: Our findings revealed the improvement of T 1 relaxation was not only because of the increase of molecular tumbling time caused by the IO@SiO2 nanocarrier but also the generated magnetic field caused by the IO core. This nanostructure with high T 1 contrast ability may open a new approach to construct high-performance T 1 contrast agent.

3.
Appl Opt ; 58(18): 4835-4845, 2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31503798

RESUMO

The imaging quality of an airborne infrared (IR) system is limited by the angular disturbance of the airborne platform. Based on the full-chain (IR scene-atmosphere-optical system-detector-airborne platform) signal transmission process, this study focused on the low-frequency sinusoidal angular disturbance features of the airborne platform and accurately calculated the point spread function caused by the angular disturbance and the IR imaging features when the IR system's different locations were dynamically simulated in a three-dimensional scene. First, the degradation mechanism of the IR imaging features resulting from the angular disturbance was analyzed from the viewpoint of scene radiation signal transmission and detector sampling. Then, the dynamic simulation in the three-dimensional scene resulting from the angular disturbance was realized by considering the geometric transformation of the spatial imaging, scale registration of the spatial sampling, radiation coupling, and angular disturbance caused by the airborne platform. Finally, the distances detected under different disturbance conditions were predicted using the established model. The obtained results provide data supporting the demonstration, verification, and optimization of the IR imaging system's design scheme.

4.
Neurochem Res ; 44(11): 2566-2576, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31535354

RESUMO

Epilepsy is a chronic neurological disease. Astrogliosis is an important pathological change in epileptic lesions. Studies have reported that ibuprofen can affect autophagy and/or inhibit cell proliferation in many diseases. This study investigated the effect and significance of ibuprofen on autophagy of astrocytes during pentylenetetrazol (PTZ) induced epilepsy. 60 male Sprague-Dawley (SD) rats were randomly divided into five groups: control group (received normal saline), PTZ group, 3-methyladenine (3-MA) + PTZ group, ibuprofen + PTZ group and 3-MA + ibuprofen + PTZ group. Dose of each agent was 35 mg/kg (PTZ), 10 mg/kg (3-MA) and 30 mg/kg (ibuprofen) and all drugs were administered intraperitoneally 15 times on alternate days (29 days). Human astrocytes were cultured in vitro. Behavioral performance (i.e., latency, grade and duration of seizures) and EEG of rats were observed and recorded. Proliferation of astrocytes was detected by CCK-8 method. Immunofluorescence and Western blot test were used to detect the expression of LC3 and GFAP. Mean number, grade and duration of seizures were markedly reduced in ibuprofen + PTZ group and 3-MA + ibuprofen + PTZ group (P < 0.05). Similarly, peak of EEG waves were markedly reduced in ibuprofen + PTZ group and 3-MA + ibuprofen + PTZ group (P < 0.05). Compared to the control group, the level of LC3 in ibuprofen group was significantly increased in vitro (P < 0.05). While, levels of LC3 were significantly higher and that of GFAP were significantly lower in ibuprofen + PTZ group (P < 0.05) compared to PTZ group in vivo. Ibuprofen reduces the proliferation of astrocytes by increasing autophagy, thus affecting the development of epilepsy. Therefore, ibuprofen may be used as an adjuvant to improve efficacy of treatment in epilepsy.

5.
Environ Pollut ; 255(Pt 1): 113214, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31541812

RESUMO

Magnetic properties of urban street dust can be used as a proxy of urban pollution. In this study, magnetic measurements on 160 street dust samples, collected from five different functional areas (industrial, traffic, commercial, residential and clean areas) in sixteen administrative districts in Shanghai, China, were systematically conducted. It is showed that magnetic carriers were predominately coarse-grain ferrimagnetic particles. Meantime, concentration-related magnetic parameters showed significant variations among the functional areas and administrative units. Magnetic susceptibility (χ) decreased in the following order: industrial area (IA) > traffic area (TA) > commercial area (CoA) > residential area (RA) > clean area (ClA). Moreover, combined with the analyses conducted using a scanning electron microscope and an energy dispersive X-ray spectrometer (SEM-EDX), it is found that spherical magnetic particles originating mainly from anthropogenic sources were abundant in industrial areas. Baoshan district, which is heavily impacted by industrial activities, showed the highest χ value among the administrative units. Additionally, the correlations of street dust χ value with population, value of industrial output and the gross domestic product (GDP) in Shanghai and other cities indicated that χ is positively correlated with the city GDP as well as the population size (PS) to some extent. This study demonstrates that magnetic parameters of street dust can be used as an effective tool for monitoring environmental pollution and industrial activities in urban environments.

6.
J Elder Abuse Negl ; : 1-23, 2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31394984

RESUMO

This study investigates how older adults perceive elder abuse and neglect in the context of migration and ageing. Based on a qualitative study of recent Chinese older immigrants in the Greater Toronto Area in Canada, it seeks to understand how migration and ageing processes, both of which engender cultural and contextual changes, shape and reshape views of elder abuse and neglect. The study argues that culture is important in older immigrants' perceptions of elder abuse and neglect, yet individuals with the same cultural roots may differ in their conceptualizations. Further, such perceptions could change through interactions with peers and non-peers in the host society, and these, in turn, can be influenced by both cultural and structural factors.

7.
Biomaterials ; 219: 119379, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31376746

RESUMO

Engineering interfacial structure of biomaterials have drawn much attention due to it can improve the diagnostic accuracy and therapy efficacy of nanomedicine, even introducing new moiety to construct theranostic agents. Nanosized magnetic resonance imaging contrast agent holds great promise for the clinical diagnosis of disease, especially tumor and brain disease. Thus, engineering its interfacial structure can form new theranostic platform to achieve effective disease diagnosis and therapy. In this study, we engineered the interfacial structure of typical MRI contrast agent, Gd2O3, to form a new theranostic agent with improved relaxivity for MRI guided synergetic chemodynamic/photothermal therapy. The synthesized Mn doped gadolinium oxide nanoplate exhibit improved T1 contrast ability due to large amount of efficient paramagnetic metal ions and synergistic enhancement caused by the exposed Mn and Gd cluster. Besides, the introduced Mn element endow this nanomedicine with the Fenton-like ability to generate OH from excess H2O2 in tumor site to achieve chemodynamic therapy (CDT). Furthermore, polydopamine engineered surface allow this nanomedicine with effective photothermal conversion ability to rise local temperature and accelerate the intratumoral Fenton process to achieve synergetic CDT/photothermal therapy (PTT). This work provides new guidance for designing magnetic resonance imaging guided synergetic CDT/PTT to achieve tumor detection and therapy.

8.
Inorg Chem ; 58(17): 11656-11663, 2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31430142

RESUMO

BaCuSiTe3 was prepared from the elements in a solid-state reaction at 973 K, followed by slow cooling to room temperature. This telluride adopts a new, hitherto unknown structure type, crystallizing in the noncentrosymmetric space group Pc with a = 7.5824(1) Å, b = 8.8440(1) Å, c = 13.1289(2) Å, ß = 122.022(1)°, and V = 746.45(2) Å3 (Z = 4). The structure consists of a complex network of two-dimensionally connected CuTe4 tetrahedra and ethane-like Si2Te6 units with a Si-Si bond. This semiconducting material has an optical band gap of 1.65 eV and a low thermal conductivity of 0.50 W m-1 K-1 at 300 K. Calculations of its optical properties revealed a moderate birefringence of 0.23 and a second-order harmonic generation response of deff = 3.4 pm V-1 in the static limit.

9.
ACS Appl Mater Interfaces ; 11(31): 27897-27905, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31298523

RESUMO

Owing to the expanding function of Li-ion transmission channels, it is important to explore the doping effects of different compounds into sulfide solid electrolytes to improve their electrochemical performances. However, it is hard to characterize the doping behaviors within sulfide solid electrolytes with low crystallinity and poor stability just by conventional crystallography analytical methods. In this work, the dielectric spectrum testing combined with other analytical methods, such as 7Li solid-state nuclear magnetic resonance, X-ray photoelectron spectroscopy, and the electrochemical method, have been applied to investigate the dual-doping behaviors of WS2 and LiBr within Li7P3S11 glass-ceramic electrolytes. This research method can not only evaluate the internal acting effect between the skeleton of sulfide solid electrolytes and the migrating kinetics of Li ions but also explore the capacitance at the interfaces of LiCoO2/sulfide solid electrolytes. The experimental results show that the number of Li ions with fast transport velocity within Li2S-P2S5-based solid electrolytes has been increased. Meanwhile, the interfacial capacitances between Li2S-P2S5-based solid electrolytes and the LiCoO2 cathode have decreased after dual-doping of WS2 and LiBr, indicating a synergetic effect for the doped Li7P3S11 glass-ceramic electrolytes in terms of the ionic conductivities and interfacial compatibilities. This work may provide a novel analytical approach to explore both the diffusion kinetics and interfacial behaviors for the solid electrolytes of lithium batteries.

10.
Inorg Chem ; 58(13): 8560-8569, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31247837

RESUMO

A family of compounds, A3BC3D2O14 (A = Ba, Pb; B = Te, Sb; C = Al, Ga, Fe, Zn; D = Si, Ge, P, V), with the Dugganite structure was prepared employing traditional solid-state chemistry methods. PXRD and Rietveld refinement studies indicate that the compounds are stabilized in P321 space group (no. 150). The compounds are found to be SHG active with values ranging from 1.9 to 15.0 × KDP. The compounds exhibit high dielectric constants and low loss in our studies. The noncentrosymmetry related properties of the new Dugganites were understood by band structure calculations. We also explored the present Dugganite-structured oxides for the development of new inorganic colored materials by substituting Co2+, Ni2+, Cu2+, and Fe3+ in place of Zn2+. Thus, substitution of Co2+ and Fe3+ together tunes the blue color of the cobalt compound to blue-green color arising from metal-to-metal charge transfer (MMCT) of Fe3+ and Co2+ ions. The tetrahedrally coordinated Ni2+ in the Dugganite imparts a magenta color.

11.
Inorg Chem ; 58(13): 8541-8550, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31247854

RESUMO

Twenty new alkali rare earth thiosilicates and thiogermanates with the general formula ALnTS4 (A = alkali metal, Ln = lanthanide, and T = Si, Ge) were grown as X-ray diffraction-quality single crystals from molten alkali chloride fluxes. These include KNdSiS4, KPrSiS4, RbLnSiS4 (Ln = Ce, Pr, Nd, Gd, Tb, Dy, and Ho), RbLaGeS4, CsLnSiS4 (Ln = La, Pr, and Nd), and CsLnGeS4 (La, Ce, Pr, Nd, Eu, Gd, and Tb). Herein, we discuss the use of a molten chloride flux growth approach for the preparation of the title compounds and their structure determination via single-crystal X-ray diffraction. In addition, we comment on the magnetic properties of RbNdSiS4, CsNdSiS4, CsNdGeS4, and CsGdGeS4, which were found to be paramagnetic for T = 2-300 K and exhibited negative Weiss temperatures with no obvious antiferromagnetic transition down to 2 K. The optical properties of CsLaGeS4 and CsNdTS4(T = Si, Ge) were measured by UV-vis spectroscopy. Second harmonic generation measurements performed on CsLaGeS4 confirmed the crystallization of the compound in the noncentrosymmetric orthorhombic space group, P212121; CsLaGeS4 was found to be SHG-active with nearly half the intensity of α-SiO2 upon irradiation with a Nd:YAG 1064 nm laser, and a semiconductor exhibiting a band gap of 3.60 eV based on UV-vis diffuse reflectance measurements.

12.
Dalton Trans ; 48(28): 10642-10651, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31232402

RESUMO

Two new oxyhalides including d0 and d10 cations, Cs4Cd2V4O12Cl4 (1) and Cs3CdV4O12Br (2), were successfully synthesized via a solid phase reaction. Their crystal structures have been determined by X-ray single crystal diffraction. Compound 1 crystallizes in space group Cm (no. 8), whereas compound 2 is found in space group Cmm2 (no. 35). The corner-shared V3O8 units and CdO2Cl4 units in the compound 1 bridge a three-dimensional network, whereas the corner-shared V4O11 polyhedron and CdO4Br2 octahedron in the compound 2 form a three-dimensional structure. All the polar groups align in one direction, which results in a favorable net polarization. Powder second harmonic generation, using 1064 nm incident radiation, indicates that they are phase-matchable with observable and strong SHG response (5 and 7 times KH2PO4, respectively). The UV-vis-NIR diffuse reflectance spectra indicate that the band gaps of the compound 1 and 2 are 3.00 eV (413 nm) and 3.13 eV (396 nm), respectively. Based on the IR and UV-vis-NIR data, the transparent range of both compounds is 0.4-10.4 µm. Furthermore, the electronic structure was also investigated by the first-principles calculations.

13.
Prep Biochem Biotechnol ; 49(8): 767-774, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31050593

RESUMO

The cell wall of carotenoids producing yeast Sporidiobolus pararoseus was broken through five different methods: acid-heating method, dimethyl sulfoxide (DMSO) method, enzymatic method, high-pressure homogenization (HPH) method, and cell autolysis method. HPH method not only brought the optimum breaking effect (wall-breaking extent of 72.3%) and the highest carotenoid extraction rate (67.2%), but also had the advantages of short-time, simple process, safe, and pollution-free. After optimization, the wall-breaking extent and the carotenoid extraction rate were enhanced to 78.3% and 82.5%, respectively. And the optimum conditions of HPH were obtained as homogenization pressure 80 MPa, bacterial liquid concentration 8% and homogenization for three times. Moreover, cell experiments demonstrated that all of the four carotenoids (ß-carotene, γ-carotene, torulene, and torularhodin) purified from intracellular products of S. pararoseus. had the effect of resistance to oxidative damage from hydrogen peroxide on SK-HEP-1 cells, and torulene showed the most notable effect among them.


Assuntos
Antioxidantes/isolamento & purificação , Antioxidantes/farmacologia , Basidiomycota/metabolismo , Carotenoides/isolamento & purificação , Carotenoides/farmacologia , Parede Celular/metabolismo , Antioxidantes/química , Antioxidantes/metabolismo , Carotenoides/química , Carotenoides/metabolismo , Linhagem Celular , Dimetil Sulfóxido/metabolismo , Calefação , Humanos , Microbiologia Industrial/métodos , Estresse Oxidativo/efeitos dos fármacos , Pressão , Leveduras/metabolismo
14.
Crit Rev Biotechnol ; 39(5): 633-647, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31055970

RESUMO

l-Leucine, as an essential branched-chain amino acid for humans and animals, has recently been attracting much attention because of its potential for a fast-growing market demand. The applicability ranges from flavor enhancers, animal feed additives and ingredients in cosmetic to specialty nutrients in pharmaceutical and medical fields. Microbial fermentation is the major method for producing l-leucine by using Escherichia coli and Corynebacterium glutamicum as host bacteria. This review gives an overview of the metabolic pathway of l-leucine (i.e. production, import and export systems) and highlights the main regulatory mechanisms of operons in E. coli and C. glutamicum l-leucine biosynthesis. We summarize here the current trends in metabolic engineering techniques and strategies for manipulating l-leucine producing strains. Finally, future perspectives to construct industrially advantageous strains are considered with respect to recent advances in biology.


Assuntos
Corynebacterium glutamicum/metabolismo , Escherichia coli/metabolismo , Leucina/biossíntese , Corynebacterium glutamicum/genética , Escherichia coli/genética , Leucina/genética , Engenharia Metabólica , Óperon
15.
J Mater Sci Mater Med ; 30(5): 53, 2019 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-31037512

RESUMO

Poly (glycerol sebacate) (PGS) is a synthetic polymeric material with the characteristics of controllable degradation, high plasticity and excellent biocompatibility. However, the time of PGS degradation is faster than that of cartilage regeneration, which limits its application in cartilage tissue engineering. Polycaprolactone (PCL), a widely used synthetic polymer, has appropriate biodegradability and higher mechanical strength. This study aims to make a scaffold from blends of fast degrading PGS and slowly degrading PCL, and to investigate its potential for cartilage tissue engineering applications. Scanning electron microscopic analysis indicated that the scaffolds provided favourable porous microstructures. In vitro degradation test showed that PGS/ PCL scaffolds acquired longer degradation time and better mechanical strength. PGS/PCL scaffolds seeded with Bone marrow-derived mesenchymal stem cells (BMSCs) and articular chondrocytes (ACCs) were cultured in vitro. Short-term in vitro experiments confirmed that both seeded cells could adhere and proliferate on the scaffold. Chondrogenic culture for cell-scaffold constructs confirmed BMSCs could differentiate into chondrocyte-like cells in PGS/PCL scaffolds. With tunable biodegradation, favorable mechanical properties and cytocompatibility, PGS/PCL scaffolds would potentially be suitable for the regeneration of cartilage tissue. Poly (glycerol sebacate) (PGS) is a synthetic polymeric material with the characteristics of controllable degradation, high plasticity and good biocompatibility. However, the time of PGS degradation is faster than that of cartilage regeneration, which limits its application in cartilage tissue engineering. Polycaprolactone(PCL), a widely used synthetic polymer, has appropriate biodegradability. This study aims to make a scaffold from blends of fast degrading PGS and slowly degrading PCL, and to investigate its potential for cartilage tissue engineering applications. Scanning electron microscopic analysis indicated that the scaffolds provided favourable porous microstructures. In vitro degradation test showed that PGS/ PCL scaffolds got longer degradation time with surface degradation nature. PGS/PCL scaffolds seeded with Bone marrow-derived mesenchymal stem cells (BMSCs) and articular chondrocytes (ACCs) were cultured in vitro under the same condition. Short-term in vitro experiments confirmed that both seed cells could adhere and proliferate on the scaffold. Chondrogenic culture for cell-scaffold constructs confirmed BMSCs could differentiate into chondrocyte-like cells and form cartilage-specific matrix in PGS/PCL scaffolds. With cytocompatibility and biodegradation profile, PGS/PCL scaffolds get great potential for cartilage tissue engineering.

16.
Int J Cardiol ; 292: 265-270, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31072634

RESUMO

BACKGROUND: Dual-energy computed tomography (DECT) can differentiate iodine from other materials through the material decomposition technique. The purpose of this study was to compare the diagnostic performance of DECT-derived iodine concentration (mg/ml) with conventional enhancement measurements (HU), in detecting left atrial appendage (LAA) thrombi and differentiating thrombi from circulatory stasis in atrial fibrillation (AF) patients referred for catheter ablation. METHODS: Consecutive patients were prospectively recruited and scanned using a third-generation dual-source CT system in dual-energy mode. Regions of interest were placed inside the filling defect in the LAA and ascending aorta (AA) of the same sections, to determine iodine concentration and the LAA/AA HU ratio. The diagnostic performance of iodine concentration and LAA/AA HU ratios were compared using transesophageal echocardiography (TEE) as the reference standard. RESULTS: Among 302 patients, 10 thrombi and 27 cases with spontaneous echo contrast (SEC) were detected by TEE. Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of iodine concentration were superior to those of LAA/AA HU ratios (iodine concentration: 99.7%, 100%, 99.7%, 90.9%, and 100% vs. LAA/AA HU ratios: 96.0%, 100%, 95.9%, 45.5%, and 100%) in detecting LAA thrombi. The area under the receiver operating characteristic curve of iodine concentration (0.996; 0.898-1.000) was significantly larger than that of the LAA/AA HU ratio (0.881; 0.733-0.964) in differentiating thrombi from circulatory stasis (p < 0.05). CONCLUSIONS: DECT-derived iodine concentration was associated with improved diagnostic accuracy compared with conventional enhancement measurements in detecting LAA thrombi and differentiating thrombi from circulatory stasis in AF patients.

17.
Int J Mol Sci ; 20(8)2019 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-31022947

RESUMO

The production of l-leucine was improved by the disruption of ltbR encoding transcriptional regulator and overexpression of the key genes (leuAilvBNCE) of the l-leucine biosynthesis pathway in Corynebacterium glutamicum XQ-9. In order to improve l-leucine production, we rationally engineered C. glutamicum to enhance l-leucine production, by improving the redox flux. On the basis of this, we manipulated the redox state of the cells by mutating the coenzyme-binding domains of acetohydroxyacid isomeroreductase encoded by ilvC, inserting NAD-specific leucine dehydrogenase, encoded by leuDH from Lysinibacillus sphaericus, and glutamate dehydrogenase encoded by rocG from Bacillus subtilis, instead of endogenous branched-chain amino acid transaminase and glutamate dehydrogenase, respectively. The yield of l-leucine reached 22.62 ± 0.17 g·L-1 by strain ΔLtbR-acetohydroxyacid isomeroreductase (AHAIR)M/ABNCME, and the concentrations of the by-products (l-valine and l-alanine) increased, compared to the strain ΔLtbR/ABNCE. Strain ΔLtbR-AHAIRMLeuDH/ABNCMLDH accumulated 22.87±0.31 g·L-1 l-leucine, but showed a drastically low l-valine accumulation (from 8.06 ± 0.35 g·L-1 to 2.72 ± 0.11 g·L-1), in comparison to strain ΔLtbR-AHAIRM/ABNCME, which indicated that LeuDH has much specificity for l-leucine synthesis but not for l-valine synthesis. Subsequently, the resultant strain ΔLtbR-AHAIRMLeuDHRocG/ABNCMLDH accumulated 23.31 ± 0.24 g·L-1 l-leucine with a glucose conversion efficiency of 0.191 g·g-1.


Assuntos
Vias Biossintéticas , Corynebacterium glutamicum/genética , Leucina/genética , Engenharia Metabólica/métodos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Corynebacterium glutamicum/metabolismo , Desidrogenase de Glutamato (NADP+)/genética , Desidrogenase de Glutamato (NADP+)/metabolismo , Cetol-Ácido Redutoisomerase/genética , Cetol-Ácido Redutoisomerase/metabolismo , Leucina/metabolismo , Leucina Desidrogenase/genética , Leucina Desidrogenase/metabolismo , Oxirredução
18.
J Ind Microbiol Biotechnol ; 46(7): 937-949, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30937555

RESUMO

Traditional amino acid producers typically exhibit the low glucose uptake rate and growth deficiency, resulting in a long fermentation time because of the accumulation of side mutations in breeding of strains. In this study, we demonstrate that the efficiency of L-lysine production in traditional L-lysine producer Corynebacterium glutamicum ZL-9 can be improved by rationally engineering glucose uptake systems. To do this, different bypasses for glucose uptake were investigated to reveal the best glucose uptake system for L-lysine production in traditional L-lysine producer. This study showed that overexpression of the key genes in PTSGlc or non-PTSGlc increased the glucose consumption, growth rate, and L-lysine production. However, increasing the function of PTSGlc in glucose uptake led to the increase of by-products, especially for plasmid-mediated expression system. Increasing the participation of non-PTSGlc in glucose utilization showed the best glucose uptake system for L-lysine production. The final strain ZL-92 with increasing the expression level of iolT1, iolT2 and ppgK could produce 201.6 ± 13.8 g/L of L-lysine with a productivity of 5.04 g/L/h and carbon yield of 0.65 g/(g glucose) in fed-batch culture. This is the first report of a rational modification of glucose uptake systems that improve the efficiency of L-lysine production through increasing the participation of non-PTSGlc in glucose utilization in traditional L-lysine producer. Similar strategies can be also used for producing other amino acids or their derivatives.


Assuntos
Corynebacterium glutamicum/metabolismo , Glucose/metabolismo , Lisina/biossíntese , Técnicas de Cultura Celular por Lotes , Transporte Biológico , Corynebacterium glutamicum/genética , Engenharia Metabólica/métodos
19.
Microb Cell Fact ; 18(1): 65, 2019 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-30943966

RESUMO

BACKGROUND: NAD(H/+) and NADP(H/+) are the most important redox cofactors in bacteria. However, the intracellular redox balance is in advantage of the cell growth and production of NAD(P)H-dependent products. RESULTS: In this paper, we rationally engineered glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and isocitrate dehydrogenase (IDH) to switch the nucleotide-cofactor specificity resulting in an increase in final titer [from 85.6 to 121.4 g L-1] and carbon yield [from 0.33 to 0.46 g (g glucose)-1] of L-lysine in strain RGI in fed-batch fermentation. To do this, we firstly analyzed the production performance of original strain JL-6, indicating that the imbalance of intracellular redox was the limiting factor for L-lysine production. Subsequently, we modified the native GAPDH and indicated that recombinant strain RG with nonnative NADP-GAPDH dramatically changed the intracellular levels of NADH and NADPH. However, L-lysine production did not significantly increase because cell growth was harmed at low NADH level. Lastly, the nonnative NAD-IDH was introduced in strain RG to increase the NADH availability and to equilibrate the intracellular redox. The resulted strain RGI showed the stable ratio of NADPH/NADH at about 1.00, which in turn improved cell growth (µmax. = 0.31 h-1) and L-lysine productivity (qLys, max. = 0.53 g g-1 h-1) as compared with strain RG (µmax. = 0.14 h-1 and qLys, max. = 0.42 g g-1 h-1). CONCLUSIONS: This is the first report of balancing the intracellular redox state by switching the nucleotide-cofactor specificity of GAPDH and IDH, thereby improving cell growth and L-lysine production.


Assuntos
Coenzimas/metabolismo , Corynebacterium glutamicum/crescimento & desenvolvimento , Corynebacterium glutamicum/metabolismo , Lisina/biossíntese , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Corynebacterium glutamicum/química , Corynebacterium glutamicum/genética , Fermentação , Glucose/metabolismo , Gliceraldeído-3-Fosfato Desidrogenases/genética , Gliceraldeído-3-Fosfato Desidrogenases/metabolismo , Isocitrato Desidrogenase/genética , Isocitrato Desidrogenase/metabolismo , Cinética , Engenharia Metabólica , NAD/metabolismo , NADP/metabolismo , Oxirredução
20.
J Invest Surg ; : 1-8, 2019 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-30894039

RESUMO

BACKGROUND: The purpose of this study was to examine the dimensional change of IVC during acute hemorrhage through a volume-controlled acute hemorrhagic shock model in swine. METHODS: Volume-controlled hemorrhage was performed in 10 adult Bama mini pigs. Enhanced CT scan and hemodynamic monitoring were performed when the cumulative blood loss volume reached 0%, 10%, 20%, 30%, and 40%. The transverse diameter (T) and anteroposterior diameter (AP) of IVC were measured in axial images. Hemodynamic parameters were obtained with Pulse Contour Cardiac Output (PiCCO) hemodynamic monitor device. Arterial blood samples were also collected for artery blood gas analysis at each time point. RESULTS: As the blood loss volume increased, the collapsibility (T/AP) and cross section area (CSA) of IVC significantly changed first in hepatic level and pre-renal level. The significant decrease of the CSA of IVC (shrink) occurred early when the blood loss volume reached only 10%, but the collapse of IVC occurred until the blood loss volume reached 30%. CONCLUSIONS: IVC shrank early but collapsed late during the acute hemorrhage in swine. The finding of collapsed IVC on CT scans suggested severe hypovolemic shock. Evaluation of the IVC at the CT scans can be an adjunctive test of the hemodynamic status in trauma patients.

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