Search

As an efficient molecular engineering approach, on-surface synthesis (OSS) defines a special opportunity to investigate intermolecular coupling at the sub-molecular level and has delivered many appealing polymers. So far, all OSS is based on the lateral covalent bonding of molecular precursors within a single molecular layer; extending OSS from two to three dimensions is yet to be realized. Herein, we address this challenge by cycloaddition between C60 and an aromatic compound. The C60 layer is assembled on the well-defined molecular network, allowing appropriate molecular orbital hybridization. Upon thermal activation, covalent coupling perpendicular to the surface via [4 + 2] cycloaddition between C60 and the phenyl ring of the molecule is realized; the resultant adduct shows frozen orientation and distinct sub-molecular feature at room temperature and further enables lateral covalent bonding via [2 + 2] cycloaddition. This work unlocks an unconventional route for bottom-up precise synthesis of three-dimensional covalently-bonded organic architectures/devices on surfaces. On-surface synthesis (OSS) defines a special opportunity to investigate intermolecular coupling at. sub-molecular level and has delivered many appealing polymers but so-far OSS is limited to the. lateral covalent bonding of molecular precursors. Here, the authors demonstrate cycloaddition. between C60 and an aromatic compound allowing covalent coupling perpendicular to the surface and multiple non-planar covalent coupling of C60. [ABSTRACT FROM AUTHOR]

Supercritical CO2 has excellent flow and heat transfer characteristics, but studies are lacking on the heat transfer characteristics of static mixers using it as a working medium. To obtain the heat transfer enhancement mechanism of supercritical CO2 within static mixers with three helical blades (TKSM), the flow and heat transfer characteristics of supercritical CO2 in horizontal and vertically upward of TKSM were determined by three-dimensional steady-state numerical simulation at Re=7,900−22,385, respectively. With other parameters fixed, lower heat flux, inlet temperature, operating pressure, or higher mass flow corresponds to higher heat transfer coefficients (h). The orthogonal test revealed that mass flow has the greatest effect on heat transfer. Besides, the results showed that the comprehensive performance evaluation criteria (PEC) of TKSM were 1.18–1.64 times and 1.25–1.47 times of Kenics static mixer (KSM) in two different states. Considering the local deterioration of the horizontal flow, the vertically upward flow was recommended with uniform temperature distributions. Compared with the horizontal flow, the heat transfer capacity of TKSM in the upward flow increases by 92.64%–119.63%, whereas the buoyancy effect decreases by 99.83%–99.97%. [ABSTRACT FROM AUTHOR]

Molecular recognition between nucleobases plays a crucial role in all kinds of biological processes. However, real-space investigation of the recognition capability of nucleobases in the presence of interfering compounds remains unexplored. Herein, based on the combination of scanning tunneling microscopy imaging and density functional theory modeling, we report the impact of the presence of melamine (M) on the formation and chirality of guanine (G)-tetrads on Au(111). Although M can interact with G by double hydrogen bonding, the Hoogsteen base pairing of G is not compromised, forming identical individual G-tetrads as would have happened without the presence of M. G-tetrads coexist with M on the surface not only in separate domains, but also within the mixture network of G-tetrads and M-dimers. Although the adsorption orientation of G-tetrads in the mixture network diversifies into two distinct angles, all G-tetrads in the network keep the same chirality, emphasizing the high preference of homochirality in such biochemical systems. [ABSTRACT FROM AUTHOR]

Key message: Here, a functional characterization of a wheat MSR has been presented: this protein makes a contribution to the plant's tolerance of abiotic stress, acting through its catalytic capacity and its modulation of ROS and ABA pathways. The molecular mechanism and function of certain members of the methionine sulfoxide reductase (MSR) gene family have been defined, however, these analyses have not included the wheat equivalents. The wheat MSR gene TaMSRA4.1 is inducible by salinity and drought stress and in this study, we demonstrate that its activity is restricted to the Met-S-SO enantiomer, and its subcellular localization is in the chloroplast. Furthermore, constitutive expression of TaMSRA4.1 enhanced the salinity and drought tolerance of wheat and Arabidopsis thaliana. In these plants constitutively expressing TaMSRA4.1, the accumulation of reactive oxygen species (ROS) was found to be influenced through the modulation of genes encoding proteins involved in ROS signaling, generation and scavenging, while the level of endogenous abscisic acid (ABA), and the sensitivity of stomatal guard cells to exogenous ABA, was increased. A yeast two-hybrid screen, bimolecular fluorescence complementation and co-immunoprecipitation assays demonstrated that heme oxygenase 1 (HO1) interacted with TaMSRA4.1, and that this interaction depended on a TaHO1 C-terminal domain. In plants subjected to salinity or drought stress, TaMSRA4.1 reversed the oxidation of TaHO1, activating ROS and ABA signaling pathways, but not in the absence of HO1. The aforementioned properties advocate TaMSRA4.1 as a candidate for plant genetic enhancement. [ABSTRACT FROM AUTHOR]

The methionine sulfoxide reductases (MSRs) are a group of thiol-dependent enzymes able to catalyze the conversion of methionine sulfoxide to methionine. Although some plant MSRs are known to act as protectants against various abiotic stresses, their activity in the model grass species Brachypodium distachyon has not been characterized as yet. Here, six B. distachyon MSR ( BdMSR) genes have been isolated; they generate eight distinct cDNAs, since two of them ( BdMSRB1 and - B5) produce a pair of alternatively spliced messages. The genes were transcribed in the root, culm, leaf and during various stages of caryopsis development. Those induced by abiotic stress (salinity, drought, low temperature, CdCl, HO and abscisic acid) harbored known stress-responsive cis elements in their promoter sequences. The heterologous expression of five of the BdMSRs (- A2, - A4, - B1.1, - B3 and - B5.1) in yeast revealed that their products gave a measure of protection against salinity, mannitol and oxidative stress. Substrate specificity analysis revealed that BdMSRB1.1 could reduce free Met-R-SO to Met. The enzymatic activities of BdMSRA4, -B1.1 and -B5.1 in transformed yeast under salt treatment have checked and increased obviously resulting in reducing more Met-SO to Met including the peptide and the free types under salt stress than those in control. [ABSTRACT FROM AUTHOR]

The wheat cultivar Shanrong no. 3 (cv. SR3) tolerates both salinity and drought stress more effectively than does its progenitor cultivar Jinan 177 (cv. JN177). When the cultivars are subjected to stress, a number of genes encoding methionine sulfoxide reductase (MSRs) are known to be upregulated in SR3. Here, a set of 12 full length Triticum aestivum MSR (TaMSR) cDNAs have been isolated from cv. SR3. The genes were transcribed in the wheat root, stem, and leaf in plants sampled at various developmental stages. Those induced by salinity and drought harbored known stress-responsive cis elements in their promoter region. The constitutive expression in Arabidopsis thaliana of four MSRs which were induced by salt and drought in microarray assay showed that the product of one (TaMSRA2) heightened the plant’s tolerance to NaCl, methylviologen (MV), and abscisic acid, that of the second (TaMSRA5) enhanced salinity tolerance, that of the third (TaMSRB1.1) increased tolerance to salinity, MV and H2O2, and that of the fourth (TaMSRB5.1) increased tolerance to both salinity and mannitol. The effect of the presence in A. thaliana of TaMSRB1.1 was to suppress the accumulation of reactive oxygen species and to increase the intracellular content of soluble sugars. [ABSTRACT FROM AUTHOR]

In eddy current testing, the law of attenuation of eddy current (EC) is of great concern. In conductive half space under the excitation of uniform magnetic field, the EC density decreases exponentially in the depth direction. However, in conductor with finite thickness tested by coil, the distribution of EC in the depth direction is more complicated. This paper studies the characteristics of EC attenuation in metallic plate of finite thickness. Simulation results show that there is an EC reflection at the bottom of plate, which changes the law of EC attenuation. A new concept, namely the equivalent attenuation coefficient, is proposed to quantify the speed of EC attenuation. The characteristics of EC attenuation are utilized to explain the nonmonotonic relation between coil voltage and plate thickness. Procedure of selecting frequency is discussed. Thereafter, measurement of plate thickness is carried out and accurate result is obtained. [ABSTRACT FROM AUTHOR]

Coordinated uptake and utilization of water and nitrogen (N) is important for high-yield and high-efficiency cultivation of winter wheat. The relationship between soil water consumption and N uptake and utilization has not previously been widely investigated. The purpose of this study was to examine the regulatory effects of different seeding rates with wide-space sowing on water consumption and N accumulation and translocation of winter wheat. A field experiment was conducted in the southeastern part of the Loess Plateau between 2016 and 2018, in which winter wheat was sown using the wide-space method (row spacing: 22–25 cm, and seedling bandwidth: 5–8 cm) and five seeding rates: 150, 225, 300, 375, and 450 kg seeds ha−1. The results showed that soil water consumption increased significantly with an increase in the seeding rate from 150–300 kg seeds ha−1, especially from the jointing to maturity stage of wheat growth. At 300 kg seeds ha−1, N translocation from the leaf and stem + sheath to the grains was significantly enhanced, which increased grain N accumulation. The maximum tiller number, water use efficiency, N uptake efficiency, and partial factor productivity from applied N were all recorded at a seeding rate of 300 kg seeds ha−1, thus, grain yield increased significantly by 6–18%. Correlation analysis showed that N accumulation from the sowing to anthesis stage, pre-anthesis N translocation, and the grain yield of winter wheat were closely related to total soil water consumption. Overall, the findings of this study have demonstrated that wide-space sowing of winter wheat at a 300 kg seeds ha−1 seeding rate improved the water use efficiency and N uptake efficiency, which in turn increased the tiller number and grain yield. [ABSTRACT FROM AUTHOR]