A Theoretical Study on the Borane-Catalyzed Reductive Amination of Aniline and Benzaldehyde with Dihydrogen: The Origins of Chemoselectivity.

Density functional theory calculations are used in this study to investigate the product selectivity and mechanism of borane-catalyzed reductive aldehyde amination by a H2 reducing agent. Knowing that different boranes yield different products, two typical boranes, (B(2,6-Cl2C6H3)(p-HC6F4)2 and B(C6F5)3), are studied. Of the seven possible pathways of B(2,6-Cl2C6H3)(p-HC6F4)2-catalyzed aldehyde amination analyzed herein, four are favorable. Three of the four favorable pathways involve imine intermediates, and the fourth is a Lewis acid-base synergistic pathway that involves amine-alcohol condensation. As for the B(C6F5)3 catalyst, it forms a highly stable Lewis adduct with aniline, which impedes the hydrogenation of imine. Therefore, the product of B(C6F5)3-catalyzed reductive amination of benzaldehyde and aniline is an imine. The linear relationship between the charge on the boron atom in the Lewis acid and the relative energies of the Lewis adduct and H2 splitting transition state indicates that this parameter determines product selectivity. Indeed, when the natural charge on boron is larger than 1, an amine is produced, whereas when the charge is less than 1, an imine is produced. Hence, the selectivity of products can be controlled by adjusting the natural charge of the boron atom in the Lewis acid catalyst.

Encapsulating NH4Br in a metal organic framework: achieving remarkable proton conduction in a wide relative humidity range.

Proton-conducting materials are key components for constructing high-energy-density electronic devices. In this work, by accumulating NH4Br into the nanospace of the classical metal organic framework MIL-101-Cr, a proton conductivity as high as 1.53 × 10-1 S cm-1 was achieved at 363 K and 100% RH. The proton conduction of NH4Br@MIL-101-Cr was also high even at lower relative humidity; for instance, it was ∼10-2 S cm-1 at 75% RH. The activation energy was calculated to be 0.11 eV for NH4Br@MIL-101-Cr, indicative of tight H-bond networks and a low barrier to proton transfer, and confirming the occurrence of pure proton conduction as well.

Wide Magnetic Thermal Memory Effect (∼55 K) Above Room Temperature Coupled to a Structure Phase Transition of Lattice Symmetry Reduction in High-Temperature Phase in an S = 1/2 Spin Chain Molecule Crystal.

One-dimensional (1D) S = 1/2 Heisenberg antiferromagnetic (AFM) chain system shows frequently a spin-Peierls-type transition owing to strong spin-lattice coupling. From high-temperature phase (HTP) to low-temperature phase (LTP), the spin chain distortion leads to the reduction in lattice symmetry in LTP, called the symmetry breaking (SB) phase transition. Herein, we report the first example of 1D S = 1/2 AFM molecular crystal, [Et3( n-Pr)N][Ni(dmit)2] (Et3( n-Pr)N+ = triethylpropylammonium, dmit2- = 2-thioxo-1,3-dithiole-4,5-dithiolate), which shows a structural phase transition with lattice symmetry increase in LTP, which is contrary to the SB phase transition. Particularly, the structure phase transition leads to magnetically bistable state with TC↑ ≈ 375 K, TC↓ ≈ 320 K, and surprisingly large thermal hysteresis (∼55 K). Additionally, LTP and HTP coexist in a temperature region near TC but not at TC in this 1D spin system. The large hysteresis is related to the huge deformation of anion stack, which needs high activation energy for the structure transformation and magnetic transition between LTP and HTP. This study would not only provide new insight into the relationship of spin-Peierls-type transition and structure phase transition but also offer a roadmap for searching molecular-scale magnetic bistable materials, which are in huge demand in future electronic, magnetic, and photonic technologies.

Phosphorescence Lifetime Imaging of Labile Zn2+ in Mitochondria via a Phosphorescent Iridium(III) Complex.

Phosphorescence lifetime Zn2+ imaging possesses the advantage over normal fluorescence imaging in offering the more accurate temporal-spatial Zn2+ information. Herein, we report a new phosphorescent cyclometalated Ir(III) complex with a Zn2+-chelator bearing 1,10-phenanthrolin acting as ancillary ligand, Zin-IrDPA, which displays the specific Zn2+-induced enhancement of phosphorescence and phosphorescence lifetime, and the mitochondria-targeting ability. Moreover, its Zn2+-induced phosphorescence lifetime enhancement factor is not affected by medium lipophilicity, viscosity, polarity, and especially ambient oxygen. The reversible tracking of introduced exogenous labile Zn2+ in MCF-7 and HeLa cells via phosphorescence imaging and phosphorescence lifetime imaging (PLIM) have been realized with Zin-IrDPA. Moreover, PLIM with Zin-IrDPA is able to track the SNOC-stimulated endogenous Zn2+ release in mitochondria.

LAMP3 plays an oncogenic role in osteosarcoma cells partially by inhibiting TP53.

BACKGROUND: Osteosarcoma (OS) is a common malignant tumor that predominantly occurs in adolescents. Its most common metastasis is to the lungs. As shown in our earlier study, lysosome-associated membrane glycoprotein 3 (LAMP3) is highly upregulated in metastatic OS. However, its role in the regulation of OS cell viability and apoptosis remains unknown. METHODS: We knocked down and overexpressed LAMP3 in OS cells and assessed the cell viability and apoptosis. Then, we investigated the expression of apoptosis-associated genes to identify the downstream gene(s) of LAMP3. RESULTS: Knockdown of LAMP3 significantly inhibited OS cell viability and promoted apoptosis. TP53, which is involved in the apoptosis pathway, was found to be highly upregulated after knockdown of LAMP3. Overexpression of LAMP3 significantly increased cell viability and abrogated apoptosis. Importantly, subsequent knockdown of TP53 partially suppressed the increased OS cell apoptosis induced by the inhibition of LAMP3, suggesting that TP53 is a key functional downstream gene of LAMP3. CONCLUSIONS: Our findings suggest that LAMP3 promotes OS cell viability and survival by regulating TP53 expression.

Dual emissions and thermochromic luminescences of isomorphic chiral twofold interpenetrated 3-D nets built from I1O2 type hybrid inorganic-organic frameworks of [NH2(CH3)2]3[Pb2X3(BDC)2] (X = Br, I).

Two pairs of MOF-based hybrid enantiomorphs, [NH2(CH3)2]3[Pb2X3(BDC)2] (H2BDC = 1,4-benzenedicarboxylic acid, X = Br or I), have been synthesized using the solvothermal reaction and then manually separated, which are labeled as 1a/1b (X = Br) and 2a/2b (X = I). The isomorphic 1a and 2a crystallize in tetragonal space group P43212, and the isomorphic 1b and 2b in the enantiomorphic space group P41212. Twofold interpenetrated three-dimensional (3-D) networks were built from two sets of equivalent I1O2 type hybrid inorganic-organic frameworks in 1a/1b and 2a/2b. Each I1O2 type hybrid inorganic-organic framework constructs by the inorganic pentagonal bipyramid-shape PbX3O4 (X = Br or I) polyhedral chains along the c-axis, which are further connected though bridged BDC2- ligands in the directions perpendicular to the c-axis. Hybrids 1a/1b and 2a/2b have been characterized by elemental analysis (C, H and N elements), thermogravimetric and powder X-ray diffraction techniques, and UV-visible absorption spectroscopy in the solid state. These hybrids show dual emissions at ambient conditions, which arise from the π-π* electron transition within the aromatic rings in the BDC2- ligands and the electron transition in the inorganic polyhedral semiconducting chains, as well as thermochromic luminescence behavior from 10 to 300 K owing to two emission bands displaying different responses to the temperature change.

Both Dielectrics and Conductance Anomalies in an Open-Framework Cobalt Phosphate.

Switchable conducting or dielectric materials, as the key component, show important technological applications in modern electrical and electronic devices, including data communication, phase shifters, varactors, and rewritable optical data storage. To explore new types of switchable conducting or dielectric materials could significantly accelerate the development of efficient electrical and electronic devices. Herein we present the first example of switchable conducting and dielectric material, which is based on an open-framework phosphate, (C2N2H10)0.5CoPO4. A reversible isostructural phase transition occurs at ∼348 K in this open-framework phosphate, to give both dielectrics and conductance anomaly around the critical temperature of phase transition. This study will provide a roadmap for searching new switchable conducting or dielectric materials as well as new applications of open-framework phosphates.

Fluorite-type coordination compound as iodide ion conductor: crystal structure and ionic conductivity.

The solid state electrolytes show a wide range of practical applications in a variety of all-solid-state electrochemical devices, and it is highly in demand to explore new types of solid state electrolyte materials. In this study, we have designed and prepared a fluorite-type coordination compound, [Mn(en)3]I2, which has been characterized by microanalysis for C, H and N elements, infrared spectrum in the wavenumber range of 4000-400 cm-1, thermogravimetric analysis and differential scanning calorimetry. The single crystal X-ray diffraction revealed that the bigger size [Mn(en)3]2+ cations build three-dimensional network in the crystal of [Mn(en)3]I2 and the smaller size iodide ions occupy the tetrahedral or octahedral cavities surrounded by the [Mn(en)3]2+ cations, featuring as the fluorite-type compound. The impedance spectra were investigated to reveal the ionic conductivity σ = 3.45 × 10-11 S cm-1 at 303 K, while σ = 1.37 × 10-6 S cm-1 at 423 K, sharply increasing by five orders of magnitude regarding to that at 303 K. The electric modulus analysis further confirmed the conductance contributed from the migration of iodide ions. This study opens a way to design and achieve new coordination compound-based ion conductors.

An open-framework manganese(ii) phosphite and its composite membranes with polyvinylidene fluoride exhibiting intrinsic water-assisted proton conductance.

Proton conducting materials have important technological applications as key components in electrochemical devices, including fuel cells, electrochemical sensors, electrochemical reactors and electrochromic displays. And the exploration of novel proton conducting materials is significant for the development of efficient electrochemical devices. In this study, we have investigated the proton conductance of an open-framework manganese(ii) phosphite, (NH4)0.59(H3O)1.41Mn5(HPO3)6 (1). The open-framework manganese(ii) phosphate shows superior water-stability and excellent thermal stability. There was intrinsic water-assisted proton conductivity with σ = 3.94 × 10-4 S cm-1 at 328 K and 98% RH. Furthermore, composite membranes have further been fabricated using polyvinylidene fluoride (PVDF) and 1, labeled as 1@PVDF-X, where the symbol X represents the mass percentage of 1 (as X%) in the composite membrane and X = 10-55%. The composite membranes display good mechanical performance and durability for practical applications, and the proton conductivity of 1@PVDF-55 reaches 3.32 × 10-5 S cm-1 in deionized water at 336 K.

Proton Conductance of a Superior Water-Stable Metal-Organic Framework and Its Composite Membrane with Poly(vinylidene fluoride).

Proton-exchange membranes (PEMs) as separators have important technological applications in electrochemical devices, including fuel cells, electrochemical sensors, electrochemical reactors, and electrochromic displays. The composite membrane of a proton-conducting metal-organic framework (MOF) and an organic polymer combines the unique physical and chemical nature of the polymer and the high proton conductivity of the MOF, bringing together the best of both components to potentially fabricate high-performance PEMs. In this study, we have investigated the proton-transport nature of a zirconium(IV) MOF, MOF-808 (1). This superior-water-stability MOF shows striking proton conductivity with σ = 7.58 × 10-3 S·cm-1 at 315 K and 99% relative humidity. The composite membranes of 1 and poly(vinylidene fluoride) (PVDF) have further been fabricated and are labeled as 1@PVDF-X, where X represents the mass percentage of 1 (as X%) in 1@PVDF-X and X = 10-55%. The composite membranes exhibit good mechanical features and durability for practical application and a considerable proton conductivity of 1.56 × 10-4 S·cm-1 in deionized water at 338 K as well. Thus, the composite membranes show promising applications as alternative PEMs in diverse electrochemical devices.

An inorganic-organic hybrid crystal with a two-step dielectric response and thermochromic luminescence.

An iodoplumbate-based hybrid crystal [C2-Apy][PbI3] (1) (C2-Apy+ = 1-ethyl-4-aminopyridinium) was synthesized and characterized structurally. Single crystal X-ray diffraction revealed that 1 crystallizes in the orthorhombic system with the space group Pnma at 150 K. Inorganic components form straight and face-sharing octahedral [PbI3]∞ chains and organic components form C2-Apy+ cations that are incorporated into the space between the inorganic chains. A temperature-dependent single crystal structure indicates that there exists an order-disorder transition of the cation. The dynamic motion of the cation strongly influences the dielectric and emission features of 1. 1 shows a two-step dielectric response. The first step dielectric response at a low frequency is caused by direct current conduction and electrode polarization which have been proved by impedance spectra. The second dielectric response at a high frequency (10 kHz to 10 MHz) is related to the order-disorder transition of the alkyl chain and the dynamic motion of pyridyl rings. In addition, 1 shows multi-band emission, and different emission bands show different trends with the temperature change, which makes 1 exhibit thermochromic luminescence properties.

Water assisted high proton conductance in a highly thermally stable and superior water-stable open-framework cobalt phosphate.

Proton-conducting materials show important technological applications as key components in energy conversion, electrochemical sensing and electrochromic devices; the exploration for new types of proton-conducting materials is crucial for the development of efficient electrochemical devices. In this study, we investigated the proton transport nature of an inorganic-organic hybrid crystal of open-framework cobalt phosphate, (C2N2H10)0.5CoPO4. The structure of the hybrid crystal consists of the [CoPO4]-∞ anionic framework, and the proton carriers, H2en2+ cations (en = ethylenediamine), are located in the pores to compensate the negative charges of the inorganic framework. The open-framework is thermally stable up to 653 K (380 °C) at least, and also shows superior water stability. The open-framework exhibits negligible conductance in an anhydrous environment even at 473 K; however, there is evident water-assisted proton conduction. The conductivity reaches 2.05 × 10-3 S cm-1 at 329 K and 98% RH. Such high proton conductivity can compete with numerous state-of-the-art MOFs/PCPs-based proton conductors, and this material has promising applications in diverse electrochemical devices.

Insight into Understanding Dielectric Behavior of a Zn-MOF Using Variable-Temperature Crystal Structures, Electrical Conductance, and Solid-State 13C NMR Spectra.

A Zn-based metal-organic framework (MOF)/porous coordination polymer (PCP), (EMIM)[Zn(SIP)] (1) (SIP3- = 5-sulfoisophthalate, EMIM+ = 1-ethyl-3-methylimidazolium), was synthesized using the ionothermal reaction. The Zn2+ ion adopts distorted square pyramid coordination geometry with five oxygen atoms from three carboxylates and one sulfo group. One of two carboxylates in SIP3- serves as a µ2-bridge ligand to link two Zn2+ ions and form the dinuclear SBU, and such SBUs are connected by SIP3- ligands to build the three-dimensional framework with rutile (rtl) topology. The cations from the ion-liquid fill the channels. This MOF/PCP shows two-step dielectric anomalies together with two-step dielectric relaxations; the variable-temperature single-crystal structure analyses disclosed the dielectric anomaly occurring at ca. 280 K is caused by an isostructural phase transition. Another dielectric anomaly is related to the dynamic disorder of the cations in the channels. Electric modulus, conductance, and variable-temperature solid-state 13C CP/MAS NMR spectra analyses revealed that two-step dielectric relaxations result from the dynamic motion of the cations as well as the direct-current conduction and electrode effect, respectively.

A Two-Dimensional Inorganic-Organic Hybrid Solid of Manganese(II) Hydrogenophosphate Showing High Proton Conductivity at Room Temperature.

The inorganic-organic hybrid metal hydrogenophosphate with a formula of (C2H10N2)[Mn2(HPO4)3](H2O) (1) shows layered crystal structure. The inorganic anion layer is built from Mn3O13 cluster units, and the interlayer spaces are filled by the charge-compensated ethylenediammonium dications together with the lattice water molecules. The thermogravimetry, variable-temperature powder X-ray diffraction, and the proton conductance under anhydrous and moisture environments were investigated for 1, disclosing that 1 shows high thermal stability and high proton transport nature, and the proton conductivity reaches to 1.64 × 10(-3) S·cm(-1) under 99%RH even at 293 K. The high proton conductivity is related to the formation of denser H-bond networks in the lattice.

Three orders of magnitude enhancement of proton conductivity of porous coordination polymers by incorporating ion-pairs into a framework.

A clathrate NH4Br@HKUST-1 has been prepared by means of soaking the metal-organic-framework, HKUST-1, in ammonium bromide saturated ethanol solution at ambient temperature. Both NH4Br@HKUST-1 and HKUST-1 show the same framework structure. The formula of the clathrate is approximately expressed as Cu3(BTC)2(NH4Br)1.15. The thermal stability of the metal-organic framework is not affected by incorporating ammonium bromide into its pores. The impedance spectra measurements were performed for both NH4Br@HKUST-1 and HKUST-1 in anhydrous and selected relative humidity environments, disclosing that the conductivity of NH4Br@HKUST-1 is enhanced by three/four orders of magnitude under the same conditions with respect to HKUST-1. This study provided an efficient strategy to achieve new high conductivity proton transport materials.

Robust Crystalline Hybrid Solid with Multiple Channels Showing High Anhydrous Proton Conductivity and a Wide Performance Temperature Range.

A proton conductor displaying high anhydrous proton conductivity (≈10(-2) S cm(-1)) and good performance over a broad temperature range is presented. This hybrid material is produced via doping HCl into open-framework chalcogenide(C2N2H10)(C2N2H9)2 Cu8 Sn3S12, and has cubopolyhedral cavities and multiple channels.

Dielectric response and anhydrous proton conductivity in a chiral framework containing a non-polar molecular rotor.

Herein, we report a chiral 3D framework with the formula [Co(HPO3)2][H2DABCO] (DABCO = 1,4-diazabicyclo[2.2.2]octane). This compound exhibits two distinct dielectric anomalies, one attributed to the transfer of protons between non-polar DABCO and the inorganic framework, and the other to the in-plane oscillatory fluctuation of the DABCO molecule. It also exhibits proton conductivity under high-temperature anhydrous conditions.

Diosgenin inhibits IL-1ß-induced expression of inflammatory mediators in human osteoarthritis chondrocytes.

It is well known that the inflammatory cytokines play important roles in osteoarthritis (OA). Diosgenin is a steroidal saponin found in several plants including Solanum and Dioscorea species and possesses diverse biological activities including anti-inflammatory properties. However, the role of diosgenin in inflammatory responses in OA chondrocytes is still unclear. Therefore, in this study, we investigated the anti-inflammatory properties of diosgenin in human OA chondrocytes. We found that diosgenin inhibited the production of nitric oxide (NO) and prostaglandin E2 (PGE2) induced by interleukin-1-beta (IL-1ß). Diosgenin significantly inhibited the IL-1ß-stimulated expression of metalloproteinase-3 (MMP-3), MMP-13, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in human OA chondrocytes. In addition, diosgenin suppressed the degradation of IκB-α in IL-1ß-induced human OA chondrocytes. Taken together, this study showed that diosgenin can effectively inhibit the IL-1ß-induced expression of inflammatory mediators, suggesting that diosgenin may be a potential agent in the treatment of OA.

Promoter hypermethylation of the cysteine protease RECK may cause metastasis of osteosarcoma.

The present study examined the role of reversion-inducing cysteine-rich protein with Kazal motifs (RECK) promoter hypermethylation as a causative factor in metastasis of osteosarcoma. Using human pathological samples, it is demonstrated that RECK, a cysteine protease that reversibly regulates expression of matrix metalloproteases like matrix metallopeptidase 9 (MMP9), is transcriptionally inhibited in osteosarcoma, especially metastatic variants. This result comes from its promoter hypermethylation, as evaluated in the present study by methylation-specific PCR reaction. The expression of RECK was also significantly diminished in the metastatic variants of osteosarcoma. This downregulation of RECK in advanced grades of osteosarcoma and metastatic grades was also associated with the increased expression of invadosome-specific markers like MMP9, phospho-FAK, and integrins, suggesting the complex contributions of RECK in the prevention of metastasis and its downregulation as a causative factor in osteosarcoma metastasis.

Shikonin protects chondrocytes from interleukin-1beta-induced apoptosis by regulating PI3K/Akt signaling pathway.

Chondrocyte apoptosis is mostly responsible for the development and progression of osteoarthritis. IL-1ß is generally served as an agent that induces chondrocyte apoptosis. Shikonin exerts its anti-inflammatory effect on cartilage protection in vivo. We aimed to explore the protective effect of shikonin on interleukin-1beta (IL-1ß)-induced chondrocyte apoptosis and the potential molecular mechanisms. Chondrocytes were isolated from the joints of newborn Sprague-Dawley rats. The MTT assay and LDH cell death assay were used to determine the cell viability and chondrocyte apoptosis was detected by Annexin-V/PI staining and nucleosomal degradation. The contents of phosphorylated-PI3K (p-PI3k), phosphorylated-Akt (p-Akt), Bcl-2, Bax, and cytochrome c were detected by Western blotting. A quantitative colorimetric assay was used to detect the caspase-3 activity. Our results showed that pretreatment with shikonin (4 µM) inhibited cytotoxicity and apoptosis induced by IL-1ß (10 ng/ml) in chondrocytes. Shikonin pretreatment also decreased the activity of IL-1ß that decreased Bcl-2 expression and levels of p-PI3K and p-Akt, and increased Bax expression, cytochrome c release, and caspase-3 activation. It also reversed the activity of IL-1ß that promoted the synthesis of matrix metalloproteinase-13 and inhibited the expression of tissue inhibitor of metalloproteinase-1 expression, with the net effect of suppressing extracellular matrix degradation. These data suggested that shikonin may protect chondrocytes from apoptosis induced by IL-1ß through the PI3K/Akt signaling pathway, by deactivating caspase-3.