Wildfire disturbance is a major driver of biogeochemical processes in Eurasian boreal forests, yet little is known about the response of soil nutrient stoichiometry to wildfire in this ecosystem. To ...fill this gap, we measured the composition of available soil nutrients and their stoichiometric ratios in a Chinese boreal forest along a gradient of fire history. In the 1-year-post-fire site, wildfire increased the relative abundances of element nitrogen (N), phosphorus (P), Sulphur (S), iron (Fe), and aluminum (Al), and reduced the abundances of element calcium (Ca), magnesium (Mg), and potassium (K). Available soil N:K, N:S, P:K, P:S, and S:K ratios were 240%, 70%, 440%, 160%, and 150% higher than the control, but N:P ratio was not significantly different. In the 11-year-post-fire site, the soil nutrient composition recovered to the pre-fire levels. Although most of the soil nutrient stoichiometry returned to pre-fire levels, soil N:P ratios became significantly higher. These results showed immediate wildfire effects on soil nutrient availability and composition were strongly related to fire severity, but such effects could be subdued by soil environment and topographical variations over time. Although wildfire effects on soil nutrients are mostly short-term, it could produce relatively long-term effects on balance between N and P.
Display omitted
•Wildfire altered soil nutrient composition and their stoichiometric ratios.•Most soil properties rapidly recovered to pre-fire levels.•Soil nutrients of 1-year-post-fire were highly correlated with fire severity.•Fire severity effects lessened with time since fire.•Soil environment and topography were more important in 11-year-post-fire.
Phenylalanine ammonia-lyase (PAL, EC 4.3.1.24) catalyzes the deamination of phenylalanine to cinnamate and ammonia, the first step of the phenylpropanoid pathway. PALs are ubiquitous in plants and ...also commonly found in fungi, but have not yet been detected in animals. Typically, PAL is encoded by a small multigene family and the presence of PAL isoforms is a common observation. PAL belongs to the 3,5-dihydro-5-methylidene-4
H
-imidazol-4-one-containing ammonia-lyase family and has been shown to exist as a tetramer. Both the forward and reverse reactions catalyzed by PALs were of great interest and have potential industrial and medical applications. This review, therefore, covers the recent developments related to the PAL gene distribution, phenylalanine ammonia-lyase gene family, structure and function study of PALs, as well as several potential applications of PALs. As a key gateway enzyme linking the phenylpropanoid secondary pathway to primary metabolism, PALs were extensively applied in heterologous hosts to produce phenylpropanoids. The review thereby highlights the synthetic potentials of PALs as a key component used in metabolic engineering and synthetic biology. Moreover, the other potential PAL applications, like enzyme replacement therapy of phenylketonuria, as a therapeutic enzyme in cancer treatment and microbial production of
l
-phenylalanine are also discussed in detail. Together these results provide a synopsis of a more global view of potential applications of PALs than previously available.
Phenylalanine ammonia-lyase, a versatile enzyme with industrial and medical applications.
Both topography and the occurrence of wildfire can strongly affect soil properties in forest successions. Although numerous studies have examined the effects of fire and topography, few have explored ...their shifting relative importance with time since fire. We measured physical, chemical, and biological soil properties in two topographic positions (north-facing and south-facing) in a Chinese boreal forest along a gradient of fire history. In the control site, topography strongly influenced soil properties, with north-facing slopes having higher soil moisture (SM), depth of organic matter layer (OML), total carbon and inorganic N concentrations, and lower pH, dissolved organic carbon (DOC) and nitrogen (DON). In the 1-year-post-fire site, wildfire erased topographic effects on soil variables, and greater changes in soil properties occurred on the north-facing slopes. The wildfire significantly increased soil pH, DON, ammonium and nitrate, and decreased SM, OML, DOC and microbial biomass, while no significant differences in soil properties appeared between high- and low-severity plots. In the 11-year-post-fire site, most soil properties were similar to the control except for microbial biomass, OML and DOC; topography again became a significant factor in explaining variations in soil properties. Fire severity was highly correlated only with soil pH in the 1-year-post-fire site, whereas topographic factors were always correlated with some soil properties in the three sites. In the 1-year-post-fire site, wildfire explained almost five times more variance than topography for most soil properties, whereas in the 11-year-post-fire site, the proportion of variance explained by topography increased and even surpassed that by wildfire. These results demonstrate that the resilience of Larix gmelinii forest soils might be controlled by wildfires in the short term but by topography in the long term.
Display omitted
•Wildfire reduced topographic effects on soil properties in the 1-year-post-fire site.•Fire severity had no significant impacts on soil properties•Soils could rapidly recover to the pre-fire state except for soil organic matter and microbes.•Correlations between fire severity and soil properties decreased over time, while those with topography increased.•Topography again exerted stronger effects on soils in the 11-year-post-fire site.
Conspectus High-nuclearity cluster-type metal complexes are a unique class of compounds, many of which have aesthetically pleasing molecular structures. Their interesting physical and chemical ...properties arise primarily from the electronic and/or magnetic interplay between the component metal ions. Among the extensive studies in the past two decades, those on lanthanide-containing clusters, lanthanide-exclusive or heterometallic with transition metal elements, are most notable. The research was driven by both the synthetic challenges for these generally elusive species and their intriguing magnetic properties, which are useful for the development of energy-efficient and environmentally friendly magnetic cooling technologies. Our efforts in this vein have been concentrated on developing rational synthetic methods for high-nuclearity lanthanide-containing clusters. By means of the now widely adopted approach of “ligand-controlled hydrolysis” of lanthanide ions, a great variety of cluster-type lanthanide hydroxide complexes had been prepared in the first half of this developing period (1999–2006). In this Account, our efforts since 2007 are summarized. These include (1) further development of synthetic strategies in order to expand the ligand scope and/or to increase the nuclearity (>25) of the cluster species and (2) magnetic studies pertinent to the pursuit of materials with a large magnetocaloric effect (MCE). Specifically, with the hope of expanding the family of ligands and producing clusters of previously unknown structures, we tested under hydrothermal or solvothermal conditions the use of readily available yet not commonly used ligands for controlling lanthanide hydrolysis; such ligands, carboxylates as mundane examples, tend to form insoluble complexes prior to any possible hydrolysis. We have also validated the use of preformed transition metal complexes as metalloligands for subsequent control of lanthanide hydrolysis toward heterometallic 3d–4f clusters. Furthermore, we demonstrated using ample examples that the presence of small anions as templates is essential to the assembly of high-nuclearity lanthanide-containing clusters and that maintaining a low concentration of the anion template(s) is a key to such success. It has been found that slow production/release of such anion templates by in situ ligand decomposition or absorption of atmospheric CO2 is effective in preventing precipitation of their lanthanide salts, allowing not only controllable lanthanide hydrolysis but also gradual and modular assembly of the giant cluster species. Magnetic studies targeting potential applications of such clusters as molecular magnetic coolers have also been conducted. The results are summarized in the second portion of this Account in an effort to establish a certain magneto–structure relationship. Of particular relevance is the possible correlation between MCE (evaluated using the isothermal magnetic entropy change, −ΔS M) and magnetic density, and the intracluster antiferromagnetic exchange coupling. We have also made some preliminary attempts at preparing processable and practically useful materials in the form of a monodisperse core–shell nanostructure. We succeeded in encapsulating a single nanosized heterometallic molecular cluster in a nanoshell of silica. It was found that such passivation not only helped stabilize the cluster but also reduced the magnetic interactions between individual clusters. These effects are reflected in the slightly enhanced value of −ΔS M for the core–shell composite over the parent unprotected cluster.
Heterometallic lanthanide–transition‐metal (4f–3d) clusters with well‐defined crystal structures integrate multiple metal centers and provide a platform for achieving synergistic catalytic effects. ...Herein, we present a strategy for enhanced hydrogen evolution by loading atomically precise 4f–3d clusters Ln52Ni56 on a CdS photoabsorber surface. Interestingly, some Ni2+ ions in the clusters Ln52Ni56 were exchanged by the Cd2+ to form Ln52Ni56−xCdx/CdS composites. Photocatalytic studies show that the efficient synergistic multipath charge separation and transfer from CdS to the Eu52Ni56−xCdx cluster enable high visible‐light‐driven hydrogen evolution at 25 353 μmol h−1 g−1. This work provides the strategy to design highly active photocatalytic hydrogen evolution catalysts by assembling heterometallic 4f–3d clusters on semiconductor materials.
Assembling lanthanide–transition‐metal (4f–3d) clusters Ln52Ni56 (Ln=Eu, Pr, Nd and Gd) onto CdS composites achieved enhanced photocatalytic H2 production. Some Ni2+ ions in the clusters were exchanged by Cd2+ to form Ln52Ni56−xCdx/CdS composites. An Eu52Ni56−xCdx/CdS species shows the highest activity of 25 353 μmol h−1 g−1 and an apparent quantum efficiency of 42.4 %.
Metal–organic frameworks (MOFs) provide a tunable platform for hierarchically integrating multiple components to effect synergistic functions that cannot be achieved in solution. Here we report the ...encapsulation of a Ni‐containing polyoxometalate (POM) Ni4(H2O)2(PW9O34)210− (Ni4P2) into two highly stable and porous phosphorescent MOFs. The proximity of Ni4P2 to multiple photosensitizers in Ni4P2@MOF allows for facile multi‐electron transfer to enable efficient visible‐light‐driven hydrogen evolution reaction (HER) with turnover numbers as high as 1476. Photophysical and electrochemical studies established the oxidative quenching of the excited photosensitizer by Ni4P2 as the initiating step of HER and explained the drastic catalytic activity difference of the two POM@MOFs. Our work shows that POM@MOF assemblies not only provide a tunable platform for designing highly effective photocatalytic HER catalysts but also facilitate detailed mechanistic understanding of HER processes.
POM & MOF work hand in hand: A tetra‐nickel‐containing polyoxometalate (POM) was encapsulated into the pores of phosphorescent metal–organic frameworks (MOFs). The hierarchical POM@MOF assemblies effect highly efficient photocatalytic hydrogen evolution reactions through facile multielectron transfer processes.
The synthetic strategy and building block about high-nuclearity lanthanide clusters are summarized, demonstrating the role of template anion in their assembly.
Display omitted
•High-nuclearity ...lanthanide clusters, because of their unique physical and chemical properties and their potential application, have attracted great much attention in different fields. Owing to the final structures of the lanthanide clusters not only sensitive to starting materials used in the synthesis, but also to reaction conditions including metal ions/ligands ratio, pH, solvents, temperature, duration, rational design and synthesis of lanthanide clusters remains a great challenge. Thus, it is necessary to review the recent advance in the assembly of high-nuclearity lanthanide clusters.•In this review, the synthesis of high-nuclearity lanthanide clusters using the anion template strategy was outlined based on recently reported results. The presence of small anionic species appears to be essential as a template for modular build-up of higher-nuclearity cluster complexes. Compared with a single-anion template, the slow release of anions, multiple anions or mixed anions as templates is more conducive to the assembly of high-nuclearity lanthanide clusters because of their dispersive effect on the positive charges of the clusters.•Based on the structures of the lanthanide clusters recently achieved, the building blocks in the lanthanide clusters were analysed. Some of the high-nuclearity lanthanide clusters with sophisticated structures are assembled from two or more types of structural motifs. Using this building block strategy, abundant clusters featuring multiple combinations of these basic motifs have appeared at a fast rate.•Perspective in future study on the high-nuclearity clusters is discussed. For the rational design and synthesis of lanthanide clusters, future investigations should focus on the assembly mechanism of the lanthanide clusters, which not only being helpful to the rational design and construction of the high-nuclearity lanthanide clusters, but also to the properties study on the high-nuclearity lanthanide clusters.
High-nuclearity lanthanide clusters have attracted much attention in different fields because of their unique physical and chemical properties and their potential applications. In this review, the synthetic strategy and building blocks for the assembly of high-nuclearity lanthanide clusters are outlined based on recently reported high-nuclearity lanthanide clusters. Perspectives for future studies on high-nuclearity lanthanide clusters are also discussed. We hope this review will provide insight into future research on high-nuclearity lanthanide clusters.
Growing evidence indicates that translational control of specific mRNAs contributes importantly to genetic regulation across the breadth of cellular and developmental processes. Synthesis of protein ...from a specific mRNA can be controlled by RNA-binding proteins at the level of translational initiation and elongation, and translational control is also sometimes coupled to mRNA localization mechanisms. Recent discoveries from invertebrate and vertebrate systems have uncovered novel modes of translational regulation, have provided new insights into how specific regulators target the general translational machinery and have identified several new links between translational control and human disease.
Intelligence has been considered as the major challenge in promoting economic potential and production efficiency of precision agriculture. In order to apply advanced deep-learning technology to ...complete various agricultural tasks in online and offline ways, a large number of crop vision datasets with domain-specific annotation are urgently needed. To encourage further progress in challenging realistic agricultural conditions, we present the CropDeep species classification and detection dataset, consisting of 31,147 images with over 49,000 annotated instances from 31 different classes. In contrast to existing vision datasets, images were collected with different cameras and equipment in greenhouses, captured in a wide variety of situations. It features visually similar species and periodic changes with more representative annotations, which have supported a stronger benchmark for deep-learning-based classification and detection. To further verify the application prospect, we provide extensive baseline experiments using state-of-the-art deep-learning classification and detection models. Results show that current deep-learning-based methods achieve well performance in classification accuracy over 99%. While current deep-learning methods achieve only 92% detection accuracy, illustrating the difficulty of the dataset and improvement room of state-of-the-art deep-learning models when applied to crops production and management. Specifically, we suggest that the YOLOv3 network has good potential application in agricultural detection tasks.
Background:Cardiac ischemia/reperfusion (I/R) injury will cause a large amount of cardiomyocyte loss and cascade reactions such as apoptosis, mitochondrial dysfunction, and excessive autophagy. ...Mesenchymal stem cells (MSCs) are promising therapeutic tools to replace damaged cardiomyocytes, but the underlying mechanism is still unknown.Methods and Results:Exosomes contain many microRNAs and protein, which are believed to have multiple biological functions. This study explored the role of bone marrow MSCs (BMMSCs)-derived exosomes under different oxidation levels in heart protection and miRNA-related mechanisms. Exosomes extracted from BMMSCs contained a high level of miR-29c, and its expression level changed after cells were treated under hypoxia/reoxygenation (H/R) conditions. In vivo I/R experiments also confirmed an expression change of miR-29c, and PTEN-Akt-mTOR is one of the predominant pathways that regulate autophagic change during this process.Conclusions:This study highlighted the role of miR-29c in regulating autophagy under cardiac I/R injury, which also extended existing mechanisms of a stem cell and its derivative to explore potential therapeutic interventions in ischemic heart diseases.
PDF
