Role of Alcoholic Hydroxyls of Dicarboxylic Acids in Regulating Nanoscale Dissolution Kinetics of Dicalcium Phosphate Dihydrate

Due to the potential shortage of phosphate (P) rock resources and a faster growth in demand for phosphate fertilizers, unraveling the kinetics of calcium phosphate (Ca–P) crystallization and dissolution is important for understanding the P mobility and bioavailability. Plants have developed different strategies, such as carboxylic acid exudation into the rhizosphere, to cope with low P bioavailability through dissolution of sparingly soluble Ca–P minerals. However, the dissolution kinetics may be more complicated in the presence of both carboxylate and hydroxyl groups in organic acids. Here in situ atomic force microscopy (AFM) is used to directly observe the kinetics of nanoscale dissolution on the (010) surface of dicalcium phosphate dihydrate (brushite, CaHPO₄·2H₂O) in the presence of succinic acid (SA, 0 alcoholic hydroxyl (−OH)), malic acid (MA, 1 −OH), and tartaric acid (TA, 2 −OH), respectively, over a broad concentration range. We demonstrate that the role of dicarboxylic acids varies with the number of alcoholic hydroxyls and that fully deprotonated hydroxy-dicarboxylic acids play a critical role in controlling the dissolution rate of steps and morphology modification of etch pits. Direct AFM imaging shows that only TA can adsorb along specific directions of the [1̅01̅]_<i>Cc</i> steps on the brushite (010) surface at pH ≥ 6 to induce the formation of trapezium-shaped etch pits. This depends on specific molecular recognition and stereochemical conformity between hydroxyl-carboxyl of TA and atomic [1̅01̅]_<i>Cc</i> steps by molecular modeling using density functional theory. The effectiveness of alcoholic hydroxyls can be enhanced by deprotonated brushite interfaces with the increase of the solution pH. This combined AFM and molecular modeling study may provide microscopic insights into understanding P mobilization by dissolution in soils

Involving online community customers in product innovation: The double-edged sword effect

Existing research in the field of business has generated differing views on the relationship between customer involvement and firms' product innovation. Drawing from their findings, some researchers have presented a positive assessment of customers' utility in product innovation, while others have provided a nonsignificant or even negative assessment of customers' usefulness in this area. This paper reconciles these different views by demonstrating that there exists a nonlinear relationship between customer involvement and firms' product innovation performance. To arrive at this conclusion, we use survey data from Chinese manufacturing firms and their online community customers, as well as objective data from the Chinese technology firm Xiaomi, to empirically test our hypothesized nonlinear relationship theory. The results of analyzing the two datasets demonstrate that there is an inverted U-shaped relationship between online customer involvement and firms' product innovation performance. Additionally, we find that customer online community affiliation moderates this relationship; specifically, for low or moderate levels of customer involvement, customer online community affiliation strengthens the positive online customer involvement–product innovation performance relationship, while for high levels of customer involvement, such customer affiliation weakens the positive impact of online customer involvement on firms' product innovation performance. Furthermore, we also show that the factor “customer online knowledge contribution” mediates the relationship between customer involvement and product innovation performance. Overall, this study provides new empirically-supported insights into the impacts of customer involvement and the contribution of customer knowledge through online communities on firms’ product innovation performance, thereby adding significant findings to the literature, as well as offering practical implications to firms regarding how they can best involve online customers in product innovation to achieve the most effective performance

Occluded Organic Nanofibers Template the Hierarchical Organization of Nanosized Particles in Calcium Oxalate Raphides of <i>Musa</i> spp

The formation of needle-shaped calcium oxalate crystals called raphides is unique to plants, in which related matrix proteins control crystallization of raphides at biomacromolecule–mineral interfaces with convoluted internal structure and complex morphology. However, investigations for understanding intermediate structures and the underlying mechanisms of raphide biomineralization have been lacking. We present a more detailed single-raphide composition by nanoscale secondary ion mass spectrometry (NanoSIMS) mapping to reveal the presence of individual organic fibers embedded inside raphides. This is in situ observed by imaging demineralization of individual raphides using atomic force microscopy (AFM) to unveil the template-mediated organized aggregation of calcium oxalate nanoparticles via a nonclassical particle-based pathway; internal structures are analyzed using high-resolution transmission electron microscopy (HRTEM) to demonstrate the multistep phase transformation by beam-induced coarsening through intermediates of nanoparticles from amorphous calcium oxalate (ACO) to calcium oxalate trihydrate (COT)/calcium oxalate dihydrate (COD) to the final product of elongated and tapered hexagonal crystals of calcium oxalate monohydrate (COM). The findings at the single-raphide level may improve the fundamental understanding of the structural and morphological complexity in biominerals evolved for survival and adaptation occurring in most plant taxa

Selective Double Carbomagnesiation of Internal Alkynes Catalyzed by Iron-N-Heterocyclic Carbene Complexes: A Convenient Method to Highly Substituted 1,3-Dienyl Magnesium Reagents

Controlled multicarbometalation of alkynes has been envisaged as an efficient synthetic method for dienyl and polyenyl metal reagents, but an effective catalyst enabling the transformation has remained elusive. Herein, we report that an iron­(II)-N-heterocyclic carbene (NHC) complex (IEt₂Me₂)₂FeCl₂ (IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) can serve as a precatalyst for the double carbometalation of internal unsymmetrical alkynes with alkyl Grignard reagents, producing highly substituted 1,3-dienyl magnesium reagents with high regio- and stereoselectivity. Mechanistic studies suggest the involvement of low-coordinate organoiron­(II)-NHC species as the in-cycle intermediates. The strong σ-donating nature of IEt₂Me₂ and its appropriate steric property are thought the key factors endowing the iron-NHC catalyst fine performance

<i>GmFW1</i> expression decreased in <i>GmSymRK</i> knockdown transgenic soybean roots

<p>SymRK and <i>GmFWL1</i> both play important roles in nodulation. However, during symbiotic development, the details of Nod factor signaling association with the regulation of cell division in nodules are unknown. SymRK, the immediately downstream component of these Nod factor receptors, is central to the Nod factor signaling cascade. In this study, specified RNAi plasmid of <i>GmSymRK</i> was constructed and transformed into soybean roots by agrobacterium rhizogenes-mediated hairy root transformation. We found that the nodule number decreased substantially in <i>GmSymRK</i> knockdown soybean transgenic roots. Further to study the relationship between <i>GmFWL1</i> and Nod factor signaling, we analyzed the <i>GmFWL1</i> expression levels in the <i>GmSymRK</i> RNAi soybean transgenic roots and found that rhizobia inoculation led to substantially reduced <i>GmFWL1</i> expression in <i>GmSymRK</i> RNAi soybean transgenic roots. Our studies showed that the regulation of cell division was affected by Nod factor signaling during nodule development in soybean, which provides important information toward understanding the functions of <i>GmSymRK</i> and <i>GmFWL1</i> in symbiotic signaling and nodule development.</p

High-Oxidation-State 3d Metal (Ti–Cu) Complexes with <i>N</i>‑Heterocyclic Carbene Ligation

High-oxidation-state 3d metal species have found a wide range of applications in modern synthetic chemistry and materials science. They are also implicated as key reactive species in biological reactions. These applications have thus prompted explorations of their formation, structure, and properties. While the traditional wisdom regarding these species was gained mainly from complexes supported by nitrogen- and oxygen-donor ligands, recent studies with <i>N</i>-heterocyclic carbenes (NHCs), which are widely used for the preparation of low-oxidation-state transition metal complexes in organometallic chemistry, have led to the preparation of a large variety of isolable high-oxidation-state 3d metal complexes with NHC ligation. Since the first report in this area in the 1990s, isolable complexes of this type have been reported for titanium­(IV), vanadium­(IV,V), chromium­(IV,V), manganese­(IV,V), iron­(III,IV,V), cobalt­(III,IV,V), nickel­(IV), and copper­(II). With the aim of providing an overview of this intriguing field, this Review summarizes our current understanding of the synthetic methods, structure and spectroscopic features, reactivity, and catalytic applications of high-oxidation-state 3d metal NHC complexes of titanium to copper. In addition to this progress, factors affecting the stability and reactivity of high-oxidation-state 3d metal NHC species are also presented, as well as perspectives on future efforts

Magnetoporation and Magnetolysis of Cancer Cells via Carbon Nanotubes Induced by Rotating Magnetic Fields

Weak magnetic fields (40 and 75 mT) were used either to enhance cell membrane poration (magnetoporation) or to ablate cultured human tumor cells (magnetolysis) by polymer-coated multiwalled carbon nanotubes, which form rotating bundles on exposure to magnetic fields. Findings of this study have potential clinical applications including enhanced tumor cell poration for targeted cancer chemotherapy and mechanical ablation of tumors

A Highly Conserved Motif within the Amelotin Protein Controls the Surface Growth of Brushite

Amelotin (AMTN) protein exerts a direct role on enamel biomineralization likely due to its binding affinity with calcium phosphates (Ca-Ps). However, the kinetics and molecular mechanisms of the AMTN–Ca-P interaction remain largely unknown. Here we used in situ atomic force microscopy (AFM) to directly image the surface growth of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO₄·2H₂O) in the presence of recombinant human AMTN. Measured step movement velocities of the DCPD (010) face show that AMTN protein promotes crystal face growth only within a limited concentration range, whereas inhibition occurs outside of this range. A peptide derived from a highly conserved and potentially phosphorylated motif (SSEEL) within the AMTN protein inhibits crystal growth similar to that of the AMTN protein at low concentration. By the use of single-molecule force spectroscopy (SMFS), we directly measure the binding of the full-length AMTN and SSEEL to the DCPD (010) face. Similar rupture forces reveal that this active SSEEL subdomain may contribute to a specific interaction with the DCPD (010) face, despite significant differences in binding energies of the full-length AMTN and SSEEL peptides to the DCPD surfaces. The findings reveal the kinetic and energetic basis for modulation of the Ca–P crystal face growth by AMTN and provide first evidence for a functional subdomain that is critical in controlling enamel biomineralization

The temperature–mortality relationship: an analysis from 31 Chinese provincial capital cities

<p>We aim to explore the Minimum Mortality Temperature (MMT) of different cities and regions, and that provides evidence for developing reasonable heat wave definition in China. The death data of 31 Chinese provincial capital cities from seven geographical regions during 2008–2013 was included in this study. In the first stage, a DLNM (Distributed Lag Non-linear Model) was used to estimate the association between mean temperature and mortality in a single city, then we pooled them with a multivariate meta-analysis to estimate the region-specific effects. The range of MMT was from 17.4 °C (Shijiazhuang) to 28.4 °C (Haikou), and the regional MMT increased as the original latitude decreased. Different cities and regions have their own specialized MMT due to geography and demographic characteristics. These findings indicate that the government deserves to adjust measures to local conditions to develop public health policies.</p

Direct Nanoscale Imaging Reveals the Mechanism by Which Organic Acids Dissolve Vivianite through Proton and Ligand Effects

The coprecipitation of iron (Fe) and phosphorus (P) in natural environments limits their bioavailability. Plant root-secreted organic acids can dissolve Fe–P precipitates, but the molecular mechanism underlying mobilizing biogenic elements from highly insoluble inorganic minerals remains poorly understood. Here, we investigated vivianite (Fe3(PO4)2·8H2O) dissolution by organic acids (oxalic acid (OA), citric acid (CA), and 2′-dehydroxymugineic acid (DMA)) at three different pH values (4.0, 6.0, and 8.0). With increasing pH, the vivianite dissolution efficiency by OA and CA was decreased while that by DMA was increased, indicating various dissolution mechanisms of different organic acids. Under acidic conditions, weak ligand OA (HC2O4– > C2O42– at pH 4.0 and C2O42– at pH 6.0) dissolved vivianite through the H+ effect to form irregular pits, but under alkaline condition (pH 8.0), the completely deprotonated OA was insufficient to dissolve vivianite. At pH 4.0, CA (H2Cit– > HCit2– > H3Cit) dissolved vivianite to form irregular pits through a proton-promoted mechanism, while at pH 6.0 (HCit2– > Cit3–) and pH 8.0 (Cit3–), CA dissolved vivianite to form near-rhombohedral pits through a ligand-promoted mechanism. At three pH values ((H0)­DMA3– > (H1)­DMA2– at pH 4.0, (H0)­DMA3– at pH 6.0, and (H0)­DMA3– and one deprotonated imino at pH 8.0), strong ligand DMA dissolved vivianite to form near-rhombohedral pits via ligand-promoted mechanisms. Raman spectroscopy showed that the deprotonated carboxyl groups (COO–) and imino groups were bound to Fe on the vivianite (010) face. The surface free energy of vivianite coated with OA decreased from 29.32 mJ m–2 to 24.23 mJ m–2 and then to 13.47 mJ m–2 with increasing pH, and that coated with CA resulted in a similar pH-dependent vivianite surface free-energy decrease while that coated with DMA increased the vivianite surface free energy from 31.92 mJ m–2 to 39.26 mJ m–2 and then to 49.93 mJ m–2. Density functional theory (DFT)-based calculations confirmed these findings. Our findings provide insight into the mechanism by which organic acids dissolved vivianite through proton and ligand effects