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DNA meiotic recombinase 1 (disrupted meiotic cDNA, Dmc1) protein is homologous to the Escherichia coli RecA protein, was first identified in Saccharomyces cerevisiae. This gene has been well studied as an essential role in meiosis in many species. However, studies on the dmc1 gene in reptiles are limited. In this study, a cDNA fragment of 1,111 bp was obtained from the gonadal tissues of the Chinese soft-shell turtle via RT-PCR, containing a 60 bp 3' UTR, a 22 bp 5' UTR, and an ORF of 1,029 bp encoding 342 amino acids, named Psdmc1. Multiple sequence alignments showed that the deduced protein has high similarity (>95 %) to tetrapod Dmc1 proteins, while being slightly lower (86-88 %) to fish species.Phylogenetic tree analysis showed that PsDmc1 was clustered with the other turtles' Dmc1 and close to the reptiles', but far away from the teleost's. RT-PCR and RT-qPCR analyses showed that the Psdmc1 gene was specifically expressed in the gonads, and much higher in testis than the ovary, especially highest in one year-old testis. In situ hybridization results showed that the Psdmc1 was mainly expressed in the perinuclear cytoplasm of primary and secondary spermatocytes, weakly in spermatogonia of the testes. These results indicated that dmc1 would be majorly involved in the developing testis, and play an essential role in the germ cells' meiosis. The findings of this study will provide a basis for further investigations on the mechanisms behind the germ cells' development and differentiation in Chinese soft-shell turtles, even in the reptiles.
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Gametogênese , Filogenia , Tartarugas , Animais , Feminino , Masculino , Sequência de Aminoácidos , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Clonagem Molecular , Gametogênese/genética , Meiose/genética , Ovário/metabolismo , Espermatócitos/metabolismo , Testículo/metabolismo , Tartarugas/genética , Tartarugas/metabolismoRESUMO
There is increased interest in ultrathin flexible devices with thicknesses of <1 micrometers due to excellent conformability toward advanced laminated bioelectronics. However, because of limitations in materials, device structure, and fabrication methodology, the performance of these ultrathin devices and circuits is insufficient to support higher-level applications. Here, we report high-performance carbon nanotube-based thin-film transistors (TFTs) and differential amplifiers on ultrathin polyimide films with a total thickness of <180 nanometers. A dual-gate structure is introduced to guarantee excellent gate control efficiency and mechanical stability of the ultrathin TFTs, which exhibit high transconductance (8.96 microsiemens per micrometer), high mobility (127 square centimeters per volt per second), and steep subthreshold swing (84 millivolts per decade), and can sustain a bending radius of curvature of <10 micrometers. The differential amplifier achieves the highest gain-bandwidth product (1.83 megahertz) among flexible differential amplifiers, enabling higher-gain amplification of weak signals over an extended frequency spectrum that is demonstrated by amplification of electromyography signals in situ.
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Evidence regarding the role of dietary patterns in metabolic syndrome (MetS) is limited. The mechanistic links between dietary patterns, insulin resistance, and MetS are not fully understood. This study aimed to evaluate the associations between dietary patterns and the risk of MetS in a Chinese population using a longitudinal design. Data from the China Health and Nutrition Survey, a nationally representative survey, were analyzed. MetS cases were identified based on biomarker data collected in 2009. Factor analysis was employed to identify dietary patterns, while logistic regression models were utilized to examine the association between dietary patterns and MetS. Mediation models were applied to assess multiple mediation effects. Two dietary patterns were revealed by factor analysis. Participants in the higher quartiles of the traditional Chinese dietary pattern had lower odds of MetS than those in the lowest quartile (Q1) (OR = 0.58, 95%CI: 0.48, 0.69 for Q4; OR = 0.75, 95%CI: 0.63, 0.89 for Q3). Conversely, participants in the higher quartiles of the modern Chinese dietary pattern had higher odds of MetS compared to those in the lowest quartile (Q1) (OR = 1.40, 95%CI: 1.17, 1.68 for Q4; OR = 1.27, 95%CI: 1.06, 1.52 for Q3). Significant associations between dietary patterns and MetS were mediated by insulin resistance. Therefore, dietary patterns in Chinese adults are associated with MetS, and these associations appear to be mediated through insulin resistance. These findings underscore the critical role of dietary patterns in the development of MetS and establish a foundation for culturally tailored dietary interventions aimed at reducing rates the prevalence of MetS among Chinese adults.
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Dieta , Resistência à Insulina , Síndrome Metabólica , Humanos , Síndrome Metabólica/epidemiologia , Feminino , Masculino , Pessoa de Meia-Idade , China/epidemiologia , Adulto , Dieta/efeitos adversos , Fatores de Risco , Povo Asiático , Idoso , Inquéritos Nutricionais , Comportamento Alimentar , Padrões Dietéticos , População do Leste AsiáticoRESUMO
Understanding the growth mechanisms of nanomaterials is crucial for effectively controlling their morphology which may affect their properties. Here, the growth process of indium nanoplates is studied using in situ liquid cell transmission electron microscopy. Quantitative analysis shows that the growth of indium nanoplate is limited by surface reaction. Besides, the growth process has two stages, which is different from that of other metal nanoplates reported previously. At the first stage, indium particles transform gradually from face-centered cubic to body-centered tetragonal (bct) structure as the seeds grow. At the second stage, the seeds grow faster than at the first stage and form indium triangular nanoplates. Indium triangular nanoplates have a bct structure with {011}-twin, which is found to form through kinetic reactions. In addition, the shape evolution of truncated triangle nanoplate with multiple twin planes is studied. The growth rate of truncated edge changes with the varied number of re-entrant grooves. The present work provides valuable insights into the growth mechanism of metal nanoplates with low-symmetric structure and the role of twin planes in the shape evolution of plate-like metal nanomaterials.
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All-solid-state lithium batteries (ASSBs) have received increasing attentions as one promising candidate for the next-generation energy storage devices. Among various solid electrolytes, sulfide-based ASSBs combined with layered oxide cathodes have emerged due to the high energy density and safety performance, even at high-voltage conditions. However, the interface compatibility issues remain to be solved at the interface between the oxide cathode and sulfide electrolyte. To circumvent this issue, we propose a simple but effective approach to magic the adverse surface alkali into a uniform oxyhalide coating on LiNi0.8Co0.1Mn0.1O2 (NCM811) via a controllable gas-solid reaction. Due to the enhancement of the close contact at interface, the ASSBs exhibit improved kinetic performance across a broad temperature range, especially at the freezing point. Besides, owing to the high-voltage tolerance of the protective layer, ASSBs demonstrate excellent cyclic stability under high cutoff voltages (500â cycles~94.0 % at 4.5â V, 200â cycles~80.4 % at 4.8â V). This work provides insights into using a high voltage stable oxyhalide coating strategy to enhance the development of high energy density ASSBs.
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Background: We aim to investigate whether the neutrophil-to-serum iron ratio (N/SI) is a promising biomarker for acute myocardial infarction group (AMI) and Gensini score. Methods: A total of 263 patients were enrolled and divided into four groups. The Gensini score was used to gauge the severity of coronary artery stenosis, and inflammatory biomarkers were calculated. Results: The N/SI was substantially higher in the AMI group than those in other groups, and N/SI was an independent risk factor for AMI. In ROC analyses, N/SI had the highest area under curve (AUC) for AMI among those inflammatory biomarkers. N/SI was also proved to be related with Gensini score. Conclusion: N/SI was discovered to be a new and effective inflammatory biomarker for AMI and Gensini score.
Peoples' health is at risk from heart illnesses. The indicators in patients' blood are often used to evaluate the severity of diseases. The authors collected 263 subjects with heart disease and reviewed their clinical data. Their blood was drawn to measure the neutrophil-to-serum iron ratio, a crucial blood biomarker. In conclusion, the level of neutrophil-to-serum iron ratio in these patients was closely associated with the stage and severity of their disease.
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Doença da Artéria Coronariana , Estenose Coronária , Infarto do Miocárdio , Humanos , Neutrófilos , Infarto do Miocárdio/diagnóstico , Biomarcadores , Ferro , Doença da Artéria Coronariana/complicaçõesRESUMO
Understanding how nanomaterials evolve during the etching process is critical in many fields. Herein, the wet chemical etching process of zinc oxide (ZnO) nanowires is studied in situ in radiolytic water via liquid cell transmission electron microscopy (LCTEM). The dissolution rate of thin nanowires is constant with reducing diameter, while thick nanowires (with the original diameter being larger than 95 nm) show complicated etching behaviors. The dissolution rate of thick nanowires is constant at the first stage and then increases. Anisotropic etching occurs at both ends of thick nanowires and distinct tips are formed. Different polarities at the two ends of the nanowire lead to differently shaped tips and different tip formation processes. The arrangement of the sidewall cones determines the macroscopic angle of the final tips. The present results are important for understanding liquid phase etching behavior in different dimensions and with different polar ends.
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To improve the phenomenon of exercise-induced fatigue that often occurs during horse racing, we previously studied the improvement in exercise tolerance by acupoint catgut embedding preconditioning in an exercise-induced fatigue rat model. We found that acupoint catgut embedding pretreatment effectively improved animal exercise tolerance. Here, by combining transcriptomics and metabolomics, we aimed to explore the underlying mechanisms of this improvement. We used blood biochemical detection combined with ELISA to detect triglyceride (TG), total cholesterol (TC), lactate dehydrogenase (LDH), high-density lipoprotein (HDL), alanine transaminase (ALT), aspartate aminotransferase (AST), and glucose (GLU), arachidonic acid (AA), and free fatty acid (FFA) content and found that acupoint embedding can correct FFA, AA, TG, LDH, and AST in the blood. We used RT-qPCR to measure the expression of genes in tissue from the quadriceps femoris muscle. We found that solute carrier family 27 member 2 (Slc27a2), fatty acid binding protein 1 (Fabp1), apolipoprotein C3 (Apoc3), and lipoprotein lipase (Lpl) genes in the peroxisome proliferator-activated receptor (PPAR) signaling pathway were important. The regulation of lipid metabolism through the PPAR signaling pathway was important for improving the exercise endurance of rats in our exercise-induced fatigue model. Therefore, we conclude that acupoint catgut embedding can not only promote body fat decomposition and reduce lactic acid accumulation but also promote the repair of tissue damage and liver damage caused by exercise fatigue. Acupoint catgut embedding regulates the PPAR signaling pathway by upregulating Lpl expression and downregulating Slc27a2, Fabp1, and Apoc3 expression to further improve body fat metabolism.
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Ferroptosis is a new type of cell death caused by iron-dependent lipid peroxidation. In recent years, it has been found that ferroptosis can promote the progression of atherosclerosis (AS). Macrophages have been proven to play multiple roles in the occurrence and development of AS. Iron is a necessary mineral that participates in different functions of macrophages under physiological conditions. But iron overload and ferroptosis in macrophages may promote the progression of AS. Herein, we summarize the role of iron overload and ferroptosis in macrophages in AS from the perspective of iron metabolism, and iron overload and ferroptosis are significant contributors to AS development.
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Aterosclerose , Ferroptose , Sobrecarga de Ferro , Humanos , Sobrecarga de Ferro/metabolismo , Ferro/metabolismo , Macrófagos/metabolismoRESUMO
Optical synapse is the basic component for optical neuromorphic computing and is attracting great attention, mainly due to its great potential in many fields, such as image recognition, artificial intelligence and artificial visual perception systems. However, optical synapse with infrared (IR) response has rarely been reported. InAs nanowires (NWs) have a direct narrow bandgap and a large surface to volume ratio, making them a promising material for IR detection. Here, we demonstrate a near-infrared (NIR) (750 to 1550 nm) optical synapse for the first time based on a poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))-coated InAs NW field-effect transistor (FET). The responsivity of the P(VDF-TrFE)-coated InAs NW FET reaches 839.3 A/W under 750 nm laser illumination, demonstrating the advantage of P(VDF-TrFE) coverage. The P(VDF-TrFE)-coated InAs NW device exhibits optical synaptic behaviors in response to NIR light pulses, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF) and a transformation from short-term plasticity (STP) to long-term plasticity (LTP). The working mechanism is attributed to the polarization effect in the ferroelectric P(VDF-TrFE) layer, which dominates the trapping and de-trapping characteristics of photogenerated holes. These findings have significant implications for the development of artificial neural networks.
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Intelligent materials with adaptive response to external stimulation lay foundation to integrate functional systems at the material level. Here, with experimental observation and numerical simulation, we report a delicate nano-electro-mechanical-opto-system naturally embedded in individual multiwall tungsten disulfide nanotubes, which generates a distinct form of in-plane van der Waals sliding ferroelectricity from the unique combination of superlubricity and piezoelectricity. The sliding ferroelectricity enables programmable photovoltaic effect using the multiwall tungsten disulfide nanotube as photovoltaic random-access memory. A complete "four-in-one" artificial vision system that synchronously achieves full functions of detecting, processing, memorizing, and powering is integrated into the nanotube devices. Both labeled supervised learning and unlabeled reinforcement learning algorithms are executable in the artificial vision system to achieve self-driven image recognition. This work provides a distinct strategy to create ferroelectricity in van der Waals materials, and demonstrates how intelligent materials can push electronic system integration at the material level.
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Due to their excellent electrical characteristics, InAs nanowires (NWs) have great potential as conducting channels in integrated circuits. However, the surface effect and loose native oxide coverage can deteriorate the performance of InAs NW transistors. Y2O3, a high-k dielectric with low Gibbs free energy, has been proposed to modify the InAs NW surface. Here, we systematically investigate the effect of Y2O3 coating on the performance of InAs NW field-effect transistors (FETs). We first explore the influence of the thermal oxidation process of Y2O3 on the performance of back-gated FETs. We then observe that the coverage of Y2O3/HfO2 bilayers on the NW decreases the hysteresis (the smallest value reaches 0.1 V), subthreshold swing (SS, down to 169 mV dec-1) and on-state resistance Ron, and increases the field-effect mobility µFE (up to 4876.1 cm2 V-1 s-1) and the on-off ratio, mainly owing to the passivation effect on the NW surface. Finally, paired top-gated NW FETs with a Y2O3/HfO2 bilayer and a single layer of HfO2 dielectric are fabricated and compared. The Y2O3/HfO2 bilayer provides better gate control (SSmin = 113 mV dec-1) under a smaller gate oxide capacitance, with an interface trap density as low as 1.93 × 1012 eV-1 cm-2. The use of the Y2O3/HfO2 stack provides an effective strategy to enhance the performance of III-V-based transistors for future applications.
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This study aimed at comparing the physicochemical characteristics, α-glucosidase inhibitory effect, and hypoglycemic activity of pectins (N-NOP and H-NOP) from peels of normal and Huanglongbing (HLB)-infected Navel oranges. Results indicated the pectins were high methoxy pectins mainly composed of homogalacturonan and rhamnogalacturonan-I. The pectins exhibited similar functional groups, surface morphology, and particle size, and had no triple-helical conformation in solution. They exerted fat and glucose absorption capacities and were mixed-type noncompetitive α-glucosidase inhibitors with IC50 values of 1.182 and 2.524 mg/ml, respectively. Both N-NOP and H-NOP showed hypoglycemic activity in alloxan-induced diabetic mice. Administration of them could promote the synthesis of hepatic glycogen and/or serum insulin to lower blood glucose levels and enhance antioxidant status to alleviate oxidative stress injury in diabetic mice. Moreover, N-NOP had higher yield, molecular weight, ζ-potential, oil holding capacity, α-glucosidase inhibitory effect and in vivo hypoglycemic activity, whereas H-NOP possessed higher uronic acid, degree of esterification, thermal stability, water holding capacity, swelling capacity, and fat absorption capacity. It could be concluded that some similarities and differences existed between N-NOP and H-NOP in physicochemical characteristics, functional properties, α-glucosidase inhibitory effects, and hypoglycemic activity. This study provides references for the basic research and application of pectins from peels of normal and HLB-infected Navel oranges. PRACTICAL APPLICATIONS: Pectin has been widely used in the food and pharmaceutical industries for several decades due to its health benefit, gelling, thickening, and emulsification performances. Diabetes mellitus is a worldwide concern in recent years. Pectins (N-NOP and H-NOP) from peels of normal and Huanglongbing (HLB)-infected Navel oranges possessed in vitro and in vivo hypoglycemic activities, indicating they were potential anti-antidiabetic substitutes of chemical drugs. Moreover, comparative understanding on the physicochemical characteristic, α-glucosidase inhibitory effect and hypoglycemic activity of pectins from peels of normal and Huanglongbing-infected Navel oranges was conducive to the recycling and utilization of Navel orange peels. Recently, the biological activity of pectin from peels of normal Navel oranges has been rarely reported, and the information on pectin from peels of Huanglongbing-infected Navel orange is rare. This study provides references for the basic research and application of pectins from peels of normal and HLB-infected Navel oranges.
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Citrus sinensis , Diabetes Mellitus Experimental , Insulinas , Aloxano , Animais , Antioxidantes , Glicemia , Citrus sinensis/química , Diabetes Mellitus Experimental/tratamento farmacológico , Inibidores de Glicosídeo Hidrolases/farmacologia , Hipoglicemiantes , Glicogênio Hepático , Camundongos , Pectinas/química , Pectinas/farmacologia , Ramnogalacturonanos , Ácidos Urônicos , alfa-GlucosidasesRESUMO
In recent years, thin layered indium selenide (In2Se3) has attracted rapidly increasing attention due to its fascinating properties and promising applications. Here, we report the temperature-driven α-ß phase transformation and the enhanced electronic property of 2H α-In2Se3. We find that 2H α-In2Se3 transforms to ß-In2Se3 when it is heated to a high temperature, and the transformation temperature increases from 550 to 650 K with the thickness decreasing from 67 to 17 nm. Additionally, annealing the sample below the phase transformation temperature can effectively improve the electronic property of a 2H α-In2Se3 field-effect transistor, including increasing the on-state current, decreasing the off-state current, and improving the subthreshold swing. After annealing, not only the contact resistance decreases significantly but also the mobility at 300 K increases more than 2 times to 45.83 cm2 V-1 s-1, which is the highest among the reported values. Our results provide an effective method to improve the electrical property and the stability of the In2Se3 nanodevices.
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We report a tunneling diode enabling efficient and dense electron emission from SiO2 with low poisoning sensitivity. Benefiting from the shallow SiO2 channel exposed to vacuum and the low electron affinity of SiO2 (0.9 eV), hot electrons tunneling into the SiO2 channel from the cathode of the diode are efficiently emitted into vacuum with much less restriction in both space and energy than those in previous tunneling electron sources. Monte Carlo simulations on the device performance show an emission efficiency as high as 87.0% and an emission density up to 3.0 × 105 A/cm2. By construction of a tunneling diode based on Si conducting filaments in electroformed SiO2, an emission efficiency up to 83.7% and an emission density up to 4.4 × 105 A/cm2 are experimentally realized. Electron emission from the devices is demonstrated to be independent of vacuum pressure from 10-4 to 10-1 Pa without poisoning.
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Wet chemical etching is a widely used process to fabricate fascinating nanomaterials, such as nanoparticles with precisely controlled size and shape. Understanding the etching mechanism and kinetic evolution process is crucial for controlling wet chemical etching. The development of in situ liquid cell transmission electron microscopy (LCTEM) enables the study on wet chemical etching with high temporal and spatial resolutions. However, there still lack a detailed literature review on the wet chemical etching studies by in situ LCTEM. In this review, we summarize the studies on wet etching nanoparticles, one-dimensional nanomaterials and nanoribbons by in situ LCTEM, including etching rate, anisotropic etching, morphology evolution process, and etching mechanism. The challenges and opportunities of in situ LCTEM are also discussed.
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Nanopartículas , Nanoestruturas , Microscopia Eletrônica de TransmissãoRESUMO
Poly-(R)-3-hydroxybutyrate (PHB) homeostasis in Ralstonia eutropha takes place at the interface of the cytosol and the hydrophobic PHB granule. PHB synthesis and degradation are therefore intimately linked to the process of granule assembly and breakdown. Unraveling this time-dependent three-dimensional process requires an understanding of the kinetics of synthesis of relevant proteins. Reverse transcriptase quantitative PCR and quantitative Western blotting were carried out on batch cultures of R. eutropha H16 in order to gain insight into how expression of the PHB-related genes phaA, phaB, phaC, phaP, phaR, phaZ1a, phaZ1b, and phaZ1c changed during a cell growth phase, a PHB production phase, and a PHB utilization phase. phaA, phaB, phaC, phaR, and phaZ1a were transcribed throughout cell growth, PHB production, and PHB degradation. PHB-mediated induction of PhaP expression was shown to occur at the transcriptional level, with transcript levels increasing during PHB production and decreasing during PHB utilization. Levels of PhaP correlated strongly with levels of PHB. Levels of phaZ1b transcript and protein increased sharply during production and decreased during degradation, but transcript accumulation did not depend on PHB production as in the case of phaP. No evidence of phaZ1c expression was found under the experimental conditions used in this study.
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Cupriavidus necator/metabolismo , Hidroxibutiratos/metabolismo , Poliésteres/metabolismo , Transcrição Gênica , Proteínas de Bactérias/metabolismo , Western Blotting , Cupriavidus necator/genética , Proteínas de Ligação a DNA/metabolismo , Fermentação , Homeostase , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Polyhydroxybutyrate (PHB) synthase catalyzes the polymerization of (R)-3-hydroxybutyryl-CoA (CoA = coenzyme A) into high molecular weight PHB. Recombinant wild-type (wt) class III synthase from Allochromatium vinosum (PhaCPhaE(Av)), antibodies to this synthase and to PHB, and [(14)C]hydroxybutyryl-CoA (HB-CoA) have been used to detect oligomeric hydroxybutyrate (HB) units covalently bound to the synthase using sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Although a distribution of products is typically observed, short (HB)(n)-bound synthases (designated species I) are most prevalent at low substrate to enzyme (S/E) ratios. Species I is similar to (HB)(n)-PhaC(Av) (n = 3-10 at minimum) recently identified using D302A-PhaCPhaE(Av) (Tian, J., Sinskey, A. J., and Stubbe, J. (2005) Biochemistry 44, 1495-1503). Species I is shown to be an intermediate in the elongation process of PHB synthesis in vitro. The reaction catalyzed by the wt synthase in vitro was further studied under two sets of conditions: at high (70000) and low (<200) S/E ratios. At high S/E ratios, kinetic analysis of the reaction of HB-CoA with the wt synthase monitored using antibodies to PhaCPhaE(Av) and Western blotting revealed the disappearance of PhaC(Av) at early time points and its reappearance as the molecular weight of the PHB approached 1.8 MDa. At low S/E ratios, species I was observed to increase with time after complete consumption of all of the HB-CoA. The results from studies under both sets of conditions suggest that an inherent property of the synthase is chain termination and reinitiation.
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Aciltransferases/química , Aciltransferases/classificação , Proteínas de Bactérias/química , Proteínas de Bactérias/classificação , Ácido 3-Hidroxibutírico/química , Ácido 3-Hidroxibutírico/metabolismo , Acil Coenzima A/química , Acil Coenzima A/metabolismo , Aciltransferases/metabolismo , Autorradiografia , Proteínas de Bactérias/metabolismo , Western Blotting , Radioisótopos de Carbono/metabolismo , Catálise , Chromatiaceae/enzimologia , Cupriavidus necator/enzimologia , Eletroforese em Gel de Poliacrilamida , Hidrólise , Cinética , Modelos Químicos , Proteínas Recombinantes/química , Proteínas Recombinantes/classificação , Proteínas Recombinantes/metabolismo , Especificidade por SubstratoRESUMO
This review focuses on nontemplate-dependent polymerases that use water-soluble substrates and convert them into water-insoluble polymers that form granules or inclusions within the cell. The initial part of the review summarizes briefly the current knowledge of polymer formation catalyzed by starch and glycogen synthases, polyphosphate kinase (a polymerase), cyanophycin synthetases, and rubber synthases. Specifically, our current understanding of their mechanisms of initiation, elongation (including granule formation), termination, remodeling, and polymer reutilization will be presented. General underlying principles that govern these types of polymerization reactions will be enumerated as a paradigm for all nontemplate-dependent polymerizations. The bulk of the review then focuses on polyhydroxyalkanoate (PHA) synthases that generate polyoxoesters. These enzymes are of interest as they generate biodegradable polymers. Our current knowledge of PHA production and utilization in vitro and in vivo as well as the contribution of many proteins to these processes will be reviewed.
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Aciltransferases/metabolismo , Biopolímeros/biossíntese , Proteínas de Bactérias , Biopolímeros/química , Glicogênio/biossíntese , Modelos Biológicos , Modelos Químicos , Proteínas de Plantas/biossíntese , Poliésteres/metabolismo , Polifosfatos/metabolismo , Solubilidade , Amido/biossínteseRESUMO
Wautersia eutropha, formerly known as Ralstonia eutropha, a gram-negative bacterium, accumulates polyhydroxybutyrate (PHB) as insoluble granules inside the cell when nutrients other than carbon are limited. In this paper, we report findings from kinetic studies of granule formation and degradation in W. eutropha H16 obtained using transmission electron microscopy (TEM). In nitrogen-limited growth medium, the phenotype of the cells at the early stages of granule formation was revealed for the first time. At the center of the cells, dark-stained "mediation elements" with small granules attached were observed. These mediation elements are proposed to serve as nucleation sites for granule initiation. TEM images also revealed that when W. eutropha cells were introduced into nitrogen-limited medium from nutrient-rich medium, the cell size increased two- to threefold, and the cells underwent additional volume changes during growth. Unbiased stereology was used to analyze the two-dimensional TEM images, from which the average volume of a W. eutropha H16 cell and the total surface area of granules per cell in nutrient-rich and PHB production media were obtained. These parameters were essential in the calculation of the concentration of proteins involved in PHB formation and utilization and their changes with time. The extent of protein coverage of the granule surface area is presented in the accompanying paper.