Preparation and characterisation of MgO: a heterogeneous basic catalyst for liquid phase reactions

We systematically studied the preparation method of magnesium oxide as cheap heterogeneous basic catalysts, and found a very simple method to obtain MgO with high surface area and high catalytic activity. Furthermore, the structure of MgO was characterized using many techniques, such as BET, TGA, XRD and SEM. The relationship of catalytic activity and structure of MgO has been investigated in detail. At last, the obtained MgO was used in the liquid phase reactions, including Meerwein-Pondorf-Verley reaction, Michael addition, Knoevenagel condensation, transesterification of vegetable oil to biodiesel and synthesis of P-Keto 1,3-dithianes. The prepared magnesium oxide catalyst was used in the liquid phase Meerwein-Pondorf-Verley reaction of benzaldehyde with alcohol. Effect of preparation method on the catalytic activity and structure of MgO has been investigated in detail. The experimental result showed that the optimal calcination temperature was 450 °C. Lithium supported magnesium oxide was also studied. Magnesium oxide obtained using a novel but simple procedure was systematically investigated as a heterogeneous base catalyst for the Michael addition and Knoevenagel condensation. The activity of MgO was studied in detail, together with the effects of solvent and of substrate on the catalytic activity for each type of reaction. A key finding is that the formation of enols affected the activity of MgO. The preparation method and activity of MgO was determined and compared with CaO. MgO was used for the first time as a heterogeneous basic catalyst to synthesis P-keto-1,3-dithianes from conjugated ynones and ynoates. It was found that MgO is an active catalyst with activity better than or comparable with previously identified homogeneous or heterogeneous catalysts for this reaction. The effect of preparation methods on the activity of MgO is described. Transesterification of vegetable oil to biodiesel with MgO as catalyst was studied at 60 °C and 200 °C, respectively. Effect of methanol-to-oil molar ratio, catalyst loading, reaction temperature and calcination temperature was investigated. 90% yield can be obtained at 60 °C for 3h, and 80% at 200 °C for 15min. The results showed that the prepared MgO was active for the synthesis of biodiesel

Integrative Modeling of Macromolecular Assemblies from Low to Near-Atomic Resolution

While conventional high-resolution techniques in structural biology are challenged by the size and flexibility of many biological assemblies, recent advances in low-resolution techniques such as cryo-electron microscopy (cryo-EM) and small angle X-ray scattering (SAXS) have opened up new avenues to define the structures of such assemblies. By systematically combining various sources of structural, biochemical and biophysical information, integrativemodeling approaches aimto provide a unified structural description of such assemblies, starting from high-resolution structures of the individual components and integrating all available information from low-resolution experimental methods. In this review, we describe integrative modeling approaches, which use complementary data from either cryo-EM or SAXS. Specifically, we focus on the popular molecular dynamics flexible fitting (MDFF) method, which has been widely used for flexible fitting into cryo-EM maps. Second, we describe hybrid molecular dynamics, Rosetta Monte-Carlo and minimum ensemble search (MES) methods that can be used to incorporate SAXS into pseudoatomic structural models. We present concise descriptions of the two methods and their most popular alternatives, along with select illustrative applications to protein/nucleic acid assemblies involved in DNA replication and repair

Opening Pathways of the DNA Clamps Proliferating Cell Nuclear Antigen and Rad9-Rad1-Hus1

Proliferating cell nuclear antigen and the checkpoint clamp Rad9-Rad1-Hus1 topologically encircle DNA and act as mobile platforms in the recruitment of proteins involved in DNA damage response and cell cycle regulation. To fulfill these vital cellular functions, both clamps need to be opened and loaded onto DNA by a clamp loader complex—a process, which involves disruption of the DNA clamp’s subunit interfaces. Herein, we compare the relative stabilities of the interfaces using the molecular mechanics Poisson−Boltzmann solvent accessible surface method. We identify the Rad9-Rad1 interface as the weakest and, therefore, most likely to open during clamp loading. We also delineate the dominant interface disruption pathways under external forces in multiple-trajectory steered molecular dynamics runs. We show that, similar to the case of protein folding, clamp opening may not proceed through a single interface breakdown mechanism. Instead, we identify an ensemble of opening pathways, some more prevalent than others, characterized by specific groups of contacts that differentially stabilize the regions of the interface and determine the spatial and temporal patterns of breakdown. In Rad9-Rad1-Hus1, the Rad9-Rad1 and Rad9-Hus1 interfaces share the same dominant unzipping pathway, whereas the Hus1-Rad1 interface is disrupted concertedly with no preferred directionality

METTL3/m6A/miRNA-873-5p Attenuated Oxidative Stress and Apoptosis in Colistin-Induced Kidney Injury by Modulating Keap1/Nrf2 Pathway

Nephrotoxicity of colistin is the major factor limiting its clinical application. However, the exact mechanism of colistin-induced nephrotoxicity is still elusive. N6-Methyladenosine (m6A) modification has been implicated in many biological processes, however, its role in colistin-induced nephrotoxicity needs to be elucidated. Mouse renal tubular epithelial cells (mRTECs) were treated with 200 μM colistin with or without METTL3 overexpression. Cells injury, m6A assay, oxidative stress and apoptosis were examined. Levels of m6A are decreased after colistin treatment in mRTECs. METTL3 is the major factor involved in abnormal m6A modification. METTL3 overexpression plays a protective role against colistin-induced oxidative stress and apoptosis. Moreover, METTL3 interacts with the microprocessor protein DGCR8 and positively modulates miR-873-5p mature process in an m6A-dependent manner. Further experiments show that miR-873-5p could regulate Keap1-Nrf2 pathway against colistin-induced oxidative stress and apoptosis. These studies revealed an important role of METTL3/m6A in colistin-induced nephrotoxicity and provide a new insight on m6A modification in drug induced toxicity

Spherical Indicatrices of a Bertrand Curve in Three Lie Groups

In this paper, new representations of a Bertrand curve pair in three dimensional Lie groups with bi-invariant metric are given. Besides, the spherical indicatrices of a Bertrand curve pair are obtain and the relations between the spherical indicatrices and new representations of Bertrand curve pair are shown.Comment: 12 page

Polyimides Crosslinked by Aromatic Molecules and Nanocomposites for High Temperature Capacitive Energy Storage

High temperature polymer-based dielectric capacitors are crucial for application in electronic power systems. However, the storage performance of conventional dielectrics polymer dramatically deteriorates due to the thermal breakdown under concurrent high temperatures and electric fields, and there are hardly reports on the causes of thermal breakdown from the aspects of the high temperature conduction loss and Joule heat dissipation. Herein, a combined strategy of crosslinking and compositing for polyimide-based nanocomposites is proposed, which minimizes the thermal breakdown by significantly inhibiting the high-temperature conduction loss and enhancing the high thermal conductivity. Furthermore, the rationale of the strategy was theoretically and experimentally verified from multiple perspectives. The charge-trapping effect is directly observed and quantitatively probed by Kelvin probe force microscopy with nano level resolution, indicating that the crosslinking network introduces local deep traps and effectively suppresses the charge transport. The thermal conductivity of the nanocomposites inhibits the high temperature thermal breakdown, which is confirmed by phase field simulations. Consequently, the optimized nanocomposites possess an ultra high discharge energy density(Ud) of 5.45 J/cm3 and 3.54 J/cm3 with a charge discharge efficiency, respectively, which outperforms the reported polyimide based dielectric nanocomposites. This work provides a scalable direction for high temperature polymer based capacitors with excellent performance

Impact of primary and secondary air supply intensity in stove on emissions of size-segregated particulate matter and carbonaceous aerosols from apple tree wood burning

In order to assess emission factors (EF) more accurately from household biomass burning, a series of laboratory controlled apple tree wood burning tests were conducted to measure the EFs of size-segregated particulate matter (PM) and carbonaceous aerosols. The controlled burning experiments were conducted with designed primary air (PA) and secondary air (SA) supply intensity. An optimum value of 7 m(3).h(-1) was found for SA, resulting the highest modified combustion efficiency (92.4 +/- 2.5%) as well as the lowest EFs of PM2.5 (0.13 +/- 0.01 g.MJ(-1)), OC (0.04 +/- 0.03 g.MJ(-1)) and EC (0.03 +/- 0.01 g.MJ(-1)). SA values of 7 and 10 m(3).h(-1) resulted the lowest EFs for all the different PM sizes. In a test with PA of 6 m(3.)h(-1) and SA of 7 m(3).h(-1), very low EFs were observed for 0C1 (8.2%), 0C2 (11.2%) and especially OP (Pyrolyzed OC) (0%, not detected), indicating nearly complete combustion under this air supply condition. Besides SA, higher PA was proved to have positive effects on PM and carbonaceous fraction emission reduction. For example, with a fixed SA of 1.5 m(3).h(-1), EFs of PM2.5 decreased from 0.64 to 0.27 g.MJ(-1) when PA increased from 6 to 15 m(3).h(-1) (P < 0.05). Similar reductions were also observed in EFs of OC, EC and size segregated PM

Evaluation of TIEGCM based on GOCE neutral density

The Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM), as one of the most advanced physical models of the Earth’s thermosphere and ionosphere, is not only widely used in scientific research, but also has essential reference value in aerospace operations. In this study, we use Gravity field and steady-state Ocean Circulation Explorer (GOCE) neutral density to evaluate the accuracy of the TIEGCM. The assessment is performed on both time and spatial scales. The time scales are conducted annually, monthly, and daily, while the spatial scales are carried out in terms of altitude, latitude, and local time. On the time scales, the performance of the TIEGCM on the monthly time scale is better than that on the annual time scale. Also, the performance on the daily time scale is better than that on the monthly time scale. The relative deviation shows a significant seasonal variation, that is, larger in winter and summer and smaller in spring and autumn. In addition, the relative deviation shows a negative correlation with F10.7 and Ap. On the spatial scale, with the increase in altitude, the average relative deviation of the model becomes larger in general. The relative deviation is usually larger at middle latitudes in the Northern Hemisphere and high latitudes in the Southern Hemisphere. Finally, on the scale of local time, the relative deviation changes more dramatically in local morning than at dusk

Case report: Rare novel MIPEP compound heterozygous variants presenting with hypertrophic cardiomyopathy, severe lactic acidosis and hypotonia in a Chinese infant

BackgroundMitochondrial intermediate peptidase, encoded by the MIPEP gene, is involved in the processing of precursor mitochondrial proteins related to oxidative phosphorylation. Only a few studies have shown that mutations in MIPEP can cause combined oxidative phosphorylation deficiency-31 (COXPD31), an autosomal recessive multisystem disorder associated with mitochondrial dysfunction. We report herein a rare case of an 8-month-old boy in China with hypertrophic cardiomyopathy (HCM), severe lactic acidosis, and hypotonia caused by novel MIPEP compound heterozygous variants.MethodsTrio-whole-exome sequencing and copy number variation sequencing were performed to identify mutated genetic loci. Sanger sequencing and quantitative real-time PCR were used to validate the candidate single nucleotide variants and copy number variants, respectively.ResultsThe proband was an 8-month-old boy with HCM, severe lactic acidosis, and hypotonia who died 2 months after his first admission. Two novel compound heterozygous variants, c.1081T > A (p. Tyr361Asn) and a whole deletion (Ex1-19 del), were found in the MIPEP gene, which were inherited from his healthy parents respectively. Additionally, his mitochondria DNA copy number was significantly reduced.ConclusionWe are the first to report a patient with rare MIPEP variants in China. Our findings expand the mutation spectrum of MIPEP, and provide insights into the genotype-phenotype relationship in COXPD31