Structural Change and Radical Generation of a Cadmium-Based Metal-Organic Framework Induced by an Electric Field.

Herein we report the structural change and radical generation of a cadmium-based metal-organic framework (Cd-MOF) induced by external electric fields. Under a weaker single electric field, different coordination modes of Cd-L lead to 3D → 2D structural change. Under stronger superposed electric fields, Cd-MOF was excited to produce a stable free radical. This study will provide a new avenue for the controlled assembly of MOFs.

Synthesis and Study of Crown Ether-Appended Tetraplatinum(II) Macrocylic Chemosensors for Cation Detection.

Two new functionalized platinum(II) rectangles, Pt1 and Pt2, were designed and synthesized from phenanthro crown ether- and biphenyl polyether-bridged bicarboxylate ligands, respectively. The fluorescence titration study of rectangles Pt1 and Pt2 with alkali- and alkaline-earth-metal cations indicated that Pt1 can selectively recognize Na+, while Pt2 has selective binding ability for Mg2+. These selectivity findings suggest that the comparative size and conformational nature of the polyether receptor cavity have a crucial influence on the cation selection.

[Fe2S2-Agx]-Hydrogenase Active-Site-Containing Coordination Polymers and Their Photocatalytic H2 Evolution Reaction Properties.

Three [Fe2S2-Agx]-hydrogenase active-site-containing coordination polymers (CPs), {[Fe2S2-Ag1](4-cpmt)2(CO)6(ClO4-)}n (1), {[Fe2S2-Ag2](4-cpmt)2(CO)6(OTf-)2(benzene)}n (2), and {[Fe2S2-Ag2](3-cpmt)2(CO)6(ClO4-)2}n (3), were obtained by a direct synthesis method from ligands [FeFe](4-cpmt)2(CO)6 [L1; 4-cpmt = (4-cyanophenyl)methanethiolate] and [FeFe](3-cpmt)2(CO)6 [L2; 3-cpmt = (3-cyanophenyl)methanethiolate] with silver salts. 1-3 represent the first examples of [FeFe]-hydrogenase-based CPs. It was worth noting that the Ag-S bonding between the Ag centers and S atoms of a [Fe2S2] cluster produced a novel [Fe2S2-Agx] (x = 1 or 2) catalytic site in all three polymers. The results of photochemical H2 generation experiments indicated that 2 and 3 containing [Fe2S2-Ag2] active sites showed obviously improved catalytic performances compared with ligands L1 and L2 and [Fe2S2-Ag1]-containing 1. This work provides a pioneering strategy for the direct synthesis of [Fe2S2]-based CPs or metal-organic frameworks.

Cd-MOF: specific adsorption selectivity for linear alkyne (propyne, 2-butyne and phenylacetylene) molecules.

The selective adsorption of APPT-Cd-MOF 1 for propyne, 2-butyne and phenylacetylene was confirmed by single-crystal analysis. In addition, the selective adsorption performance of Cd-MOF for C3H4/C3H6/C3H8 was investigated. The matching of the functionality and size/shape between porous materials and guest molecules clarified the specific recognition of 1 for linear alkyne molecules.

An injectable hydrogel using an immunomodulating gelator for amplified tumor immunotherapy by blocking the arginase pathway.

Arginase 1 (ARG1) inactivates T cells by degrading L-arginine, severely reducing the immunotherapeutic efficacy. Effectively blocking the ARG1 pathway remains a challenge. L-norvaline is a very cheap and negligible side effects inhibitor of ARG1. However, its blockage efficacy for ARG1 is impeded by its high half-maximal-inhibitory concentration (IC50) requiring high drug loading content of L-norvaline in carriers. Moreover its high water solubility results in bursting and uncontrolled release. Herein we reported an injectable hydrogel strategy via an L-norvaline-based immunomodulating gelator that could effectively block ARG1 pathway. The designed gelator was a diblock copolymer containing L-norvaline-based polypeptide block, which could construct a thermally responsive injectable hydrogel by its self-gelation in tumor microenvironments. The hydrogel not only ensures high drug loading of L-norvaline, but also ensures controlled release of L-norvaline through responsive peptide bond cleavage, thereby solving the problems encountered by L-norvaline. The injectable hydrogel in combination with doxorubicin hydrochloride demonstrated a potent immunotherapy for removal of primary tumors, suppression of abscopal tumors and inhibition of pulmonary metastasis by combining the blockage of ARG1 pathway and the immunogenic cell death. Our immunomodulating gelator strategy provides a robust injectable hydrogel platform to efficiently reverse ARG1 immunosuppressive environments for amplified immunotherapy. STATEMENT OF SIGNIFICANCE: We designed an injectable hydrogel via an L-norvaline-based immunomodulating gelator. The designed gelator, a diblock copolymer containing an L-norvaline-based polypeptide block, enabled a thermally responsive injectable hydrogel by its self-gelation in tumor microenvironments. The injectable hydrogel not only guarantees high drug loading of L-norvaline, but also ensures controlled release of L-norvaline through responsive peptide bonds cleavage, thereby solving the problems encountered by L-norvaline. By further introducing doxorubicin hydrochloride in the hydrogel for inducing immunogenic cell death, the hydrogel showed remarkable immunotherapeutic efficacy towards ablation of primary tumors, suppression of abscopal tumors and inhibition of pulmonary metastasis. Our immunomodulating gelator strategy provides a new concept to efficiently reverse Arginase 1 immunosuppressive environments for amplified immunotherapy.

Cu-MOF chemodynamic nanoplatform via modulating glutathione and H2O2 in tumor microenvironment for amplified cancer therapy.

Chemodynamic therapy (CDT) utilizes Fenton catalysts to convert intracellular hydrogen peroxide (H2O2) into cytotoxic hydroxyl radical (OH∙) for tumor therapy, but endogenous H2O2 is usually insufficient to achieve satisfactory tumor therapy effect. Engineering an efficient CDT nanoplatform for satisfactory cancer therapy remains a challenge. Herein, we rationally designed a Cu-based metal-organic framework-199 (MOF-199) nanoplatform integrating vitamin k3 (Vk3) for amplified CDT-mediated cancer therapy, which could accumulate efficiently in tumor tissues through enhanced permeability and retention (EPR) effect. The MOF-199 nanoparticles (MOF-199 NPs) were dissociated by glutathione (GSH) into MOF-199 fragments, which triggered Fenton-like reaction for CDT. On the one hand, Vk3 was catalyzed by NAD(P)H quinone oxidoreductase-1 (NQO1) to produce sufficient H2O2 to activate Fenton-like reaction. On the other hand, GSH was largely consumed in the tumor microenvironment. Thus, this nanoplatform enabled sufficient cytotoxic reactive oxygen species (ROS) for amplified CDT effect, demonstrating effective tumor growth inhibition with minimal side-effect in vivo. Our work provides an innovative strategy to modulate GSH and H2O2 levels for amplified CDT.

Rational Design of High-Relaxivity EuII -Based Contrast Agents for Magnetic Resonance Imaging of Low-Oxygen Environments.

Metal-based contrast agents for magnetic resonance imaging present a promising avenue to image hypoxia. EuII -based contrast agents have a unique biologically relevant redox couple, EuII/III , that distinguishes this metal for use in hypoxia imaging. To that end, we investigated a strategy to enhance the contrast-enhancing capabilities of EuII -based cryptates in magnetic resonance imaging by controlling the rotational dynamics. Two dimetallic, EuII -containing cryptates were synthesized to test the efficacy of rigid versus flexible coupling strategies. A flexible strategy to dimerization led to a modest (114 %) increase in contrast enhancement per Eu ion (60 MHz, 298 K), but a rigid linking strategy led to an excellent (186 %) increase in contrast enhancement despite this compound's having the smaller molecular mass of the two dimetallic complexes. We envision the rigid linking strategy to be useful in the future design of potent EuII -based contrast agents for magnetic resonance imaging.

Photochromic Rhenium-Based Molecular Rectangles: Syntheses, Structures, Photophysical Properties, and Electrochemistry.

Two novel fac-Re(CO)3-based rectangles {[(CO)3Re(µ-Cl)2Re(CO)3]2(µ-L)2} (1) and {[(CO)3Re(µ-OC4H9)2Re(CO)3]2(µ-L)2}(2) based on new photochromic dithienylethene-containing ligand 2,7-di(pyridin-4-yl)-9,10-bis(5-chloro-2-methylthien-3-yl)-phenanthrene (L) were prepared. They displayed varying photochromic properties both in solution and in the single-crystal state. Through a judicious choice of the bridging ligands along the short sides of the rectangles, the photophysical and electrochemical properties of the complexes could also be readily tuned.

Exploration of Recombinant Fusion Proteins YAPO and YAPL as Carrier Proteins for Glycoconjugate Vaccine Design against Streptococcus pneumoniae Infection.

Pneumolysin (Ply), pneumococcal surface protein A (PspA), and pneumococcal surface adhesin A (PsaA) are promising cell surface protein antigen targets for Streptococcus pneumoniae (Spn) vaccine development. Herein, we designed and recombined two fusion proteins, named YAPO and YAPL, which contained the main antigenic epitopes of Ply, PspA, and PsaA. In-depth immunological evaluations revealed that YAPO and YAPL had strong immunocompetence to be well-qualified potential carrier proteins. To verify this possibility, a serotype 3 Spn (ST3) CPS pentasaccharide was conjugated to each fusion protein to generate the resultant glycoconjugates. Immunological studies in mice revealed that, as compared with TT conjugate, YAPO and YAPL conjugates provoked robust T-cell dependent immune responses that could provide better recognition, in vitro efficient opsonophagocytosis, and in vivo effective protection against various serotypes of Spn. Collectively, YAPO and YAPL were identified as immunopotentiating carriers that could help convert immunologically inactive ST3 pentasaccharide into a T cell-dependent antigen and provide efficient and broad spectrum of immunoprotection coverage so as to formulate functional glycoconjugate vaccines against Spn infections.

Syntheses of four porous 3-D Cd(ii) metal-organic frameworks from a new multidentate ligand 5-(imidazol-1-yl)-N'-(pyridin-4-ylmethylene) nicotinohydrazide and their characterization and adsorption properties.

Herein, a new multidentate ligand, 5-(imidazol-1-yl)-N'-(pyridin-4-ylmethylene) nicotinohydrazide (L), with an acylhydrazone group was synthesized and characterized. Subsequently, four porous Cd(ii)-MOFs, i.e. [Cd(L)(NO3)] n (1), [Cd(L)Cl] n (2), [Cd(L)Br] n (3), and [Cd(L)I] n (4), were assembled using the ligand L by a solvothermal method and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Structural analysis shows that the coordination environments around Cd(ii) in all the four compounds are different due to the different coordinated anions. Among them, the coordination geometries and the arrangement of five-coordinated groups of the compound 1 containing the coordinated NO3 - anions are significantly different from those of the other three compounds containing halides. However, all the four MOFs have similar one-dimensional rhombic channels. In these channels, both the nitrate ions and the halide ions are attached to the inner walls of the pores. The CO2 adsorption properties of 1-4 were studied at 273 K, and the results showed that these compounds exhibit different adsorption capacities for CO2 due to the presence of different ions in their pores.

Exploring the broad nucleotide triphosphate and sugar-1-phosphate specificity of thymidylyltransferase Cps23FL from Streptococcus pneumonia serotype 23F.

Glucose-1-phosphate thymidylyltransferase (Cps23FL) from Streptococcus pneumonia serotype 23F is the initial enzyme that catalyses the thymidylyl transfer reaction in prokaryotic deoxythymidine diphosphate-l-rhamnose (dTDP-Rha) biosynthetic pathway. In this study, the broad substrate specificity of Cps23FL towards six glucose-1-phosphates and nine nucleoside triphosphates as substrates was systematically explored, eventually providing access to nineteen sugar nucleotide analogs.

Syntheses and characterization of dinuclear and tetranuclear AgI supramolecular complexes generated from symmetric and asymmetric molecular clips containing oxadiazole rings.

A new asymmetric ligand, 5-{3-[5-(4-methylphenyl)-1,3,4-oxadiazol-2-yl]phenyl}-2-(pyridin-3-yl)-1,3,4-oxadiazole (L5), which contains two oxadiazole rings, was synthesized and characterized. The assembly of symmetric 2,5-bis(pyridin-3-yl)-1,3,4-oxadiazole (L1) and asymmetric L5 with AgCO2CF3 in solution yielded two novel AgI complexes, namely catena-poly[[di-µ-trifluoroacetato-disilver(I)]-bis[µ-2,5-bis(pyridin-3-yl)-1,3,4-oxadiazole]], [Ag2(C2F3O2)2(C12H8N4O)2]n or [Ag2(µ2-O2CCF3)2(L1)2]n (1), and bis(µ3-5-{3-[5-(4-methylphenyl)-1,3,4-oxadiazol-2-yl]phenyl}-2-(pyridin-3-yl)-1,3,4-oxadiazole)tetra-µ3-trifluoroacetato-tetrasilver(I) dichloromethane monosolvate, [Ag4(C2F3O2)4(C22H15N5O2)2]·CH2Cl2 or [Ag2(µ3-O2CCF3)2(L5)]2·CH2Cl2 (2). Complex 1 displays a one-dimensional ring-chain motif, where dinuclear Ag2(CF3CO2)2 units alternate with Ag2(L1)2 macrocycles. This structure is different from previously reported Ag-L1 complexes with different anions. Complex 2 features a tetranuclear supramolecular macrocycle, in which each ligand adopts a tridentate coordination mode with the oxadiazole ring next to the p-tolyl ring coordinated and that next to the pyridyl ring free. Two L5 ligands are bound to two Ag1 centres through two oxadiazole N and two pyridyl N atoms to form a macrocycle. The other two oxadiazole N atoms coordinate to the two Ag2 centres of the Ag2(O2CCF3)4 dimer. Each CF3CO2- anion adopts a µ3-coordination mode, bridging the Ag1 and Ag2 centres to form a tetranuclear silver(I) complex. This study indicates that the donor ability of the bridging oxadiazole rings can be tuned by electron-withdrawing and -donating substituents. The emission properties of ligands L1 and L5 and complexes 1 and 2 were also investigated in the solid state.

Adsorption behaviour of a CdII-triazole MOF for butan-2-one in a single-crystal-to-single-crystal (SCSC) fashion: the role of hydrogen bonding and C-H...π interactions.

The adsorption behaviour of the CdII-MOF {[Cd(L)2(ClO4)2]·H2O (1), where L is 4-amino-3,5-bis[3-(pyridin-4-yl)phenyl]-1,2,4-triazole, for butan-2-one was investigated in a single-crystal-to-single-crystal (SCSC) fashion. A new host-guest system that encapsulated butan-2-one molecules, namely poly[[bis{µ3-4-amino-3,5-bis[3-(pyridin-4-yl)phenyl]-1,2,4-triazole}cadmium(II)] bis(perchlorate) butanone sesquisolvate], {[Cd(C24H18N6)2](ClO4)2·1.5C4H8O}n, denoted C4H8O@Cd-MOF (2), was obtained via an SCSC transformation. MOF 2 crystallizes in the tetragonal space group P43212. The specific binding sites for butan-2-one in the host were determined by single-crystal X-ray diffraction studies. N-H...O and C-H...O hydrogen-bonding interactions and C-H...π interactions between the framework, ClO4- anions and guest molecules co-operatively bind 1.5 butan-2-one molecules within the channels. The adsorption behaviour was further evidenced by 1H NMR, IR, TGA and powder X-ray diffraction experiments, which are consistent with the single-crystal X-ray analysis. A 1H NMR experiment demonstrates that the supramolecular interactions between the framework, ClO4- anions and guest molecules in MOF 2 lead to a high butan-2-one uptake in the channel.

The effect of the coordination orientation of N atoms on polymeric structures: synthesis and characterization of one- and two-dimensional CuII coordination polymers based on 4-amino-3-(pyridin-2-yl)-5-[(pyridin-3-ylmethyl)sulfanyl]-1,2,4-triazole.

Three new one- (1D) and two-dimensional (2D) CuII coordination polymers, namely poly[[bis{µ2-4-amino-3-(pyridin-2-yl)-5-[(pyridin-3-ylmethyl)sulfanyl]-1,2,4-triazole}copper(II)] bis(methanesulfonate) tetrahydrate], {[Cu(C13H12N5S)2](CH3SO3)2·4H2O}n (1), catena-poly[[copper(II)-bis{µ2-4-amino-3-(pyridin-2-yl)-5-[(pyridin-4-ylmethyl)sulfanyl]-1,2,4-triazole}] dinitrate methanol disolvate], {[Cu(C13H12N5S)2](NO3)2·2CH3OH}n (2), and catena-poly[[copper(II)-bis{µ2-4-amino-3-(pyridin-2-yl)-5-[(pyridin-4-ylmethyl)sulfanyl]-1,2,4-triazole}] bis(perchlorate) monohydrate], {[Cu(C13H12N5S)2](ClO4)2·H2O}n (3), were obtained from 4-amino-3-(pyridin-2-yl)-5-[(pyridin-3-ylmethyl)sulfanyl]-1,2,4-triazole with pyridin-3-yl terminal groups and from 4-amino-3-(pyridin-2-yl)-5-[(pyridin-4-ylmethyl)sulfanyl]-1,2,4-triazole with pyridin-4-yl terminal groups. Compound 1 displays a 2D net-like structure. The 2D layers are further linked through hydrogen bonds between methanesulfonate anions and amino groups on the framework and guest H2O molecules in the lattice to form a three-dimensional (3D) structure. Compound 2 and 3 exhibit 1D chain structures, in which the complicated hydrogen-bonding interactions play an important role in the formation of the 3D network. These experimental results indicate that the coordination orientation of the heteroatoms on the ligands has a great influence on the polymeric structures. Moreover, the selection of different counter-anions, together with the inclusion of different guest solvent molecules, would also have a great effect on the hydrogen-bonding systems in the crystal structures.

[Ag-Ag]2+ Unit-Encapsulated Trimetallic Cages: One-Pot Syntheses and Modulation of Argentophilic Interactions by the Uncoordinated Substituents.

Four [Ag-Ag]2+ unit-encapsulated trimetallic cages 1-4 were synthesized from one new tripodal ligand L and silver salts in different solvent systems by a one-pot method. The formation of coordination cages occurred simultaneously with the condensation of amino groups and ketone. The remarkable structural feature of cages 1-4 is their spontaneous incorporation of [Ag-Ag]2+ cationic units. Moreover, the argentophilic interactions are modulated by the uncoordinated amino substituents. The study herein shows that modification and subtle changes of the cage structures could be realized by a one-pot synthetic method.

Biochemical studies of a ß-1,4-rhamnoslytransferase from Streptococcus pneumonia serotype 23F.

A new ß-rhamnoslytransferase Cps23FT from Streptococcus pneumonia serotype 23F was expressed and characterized. Its enzymatic activity and function were confirmed for the first time by utilizing enzymatically prepared dTDP-Rha and chemically synthesized Glcα-PP-(CH2)11-OPh as substrates. This reaction gave the desired disaccharide Rhaß-1,4-Glcα-PP-(CH2)11-OPh in a good isolated yield (67%), suggesting the potential of Cps23FT as a tool enzyme for the synthesis of complex oligosaccharides containing difficult ß-rhamnosyl linkages. Furthermore, site-directed mutagenesis of Cps23FT disclosed that its 271DKD273 motif was critical for the enzymatic activity and most likely the binding site for the required divalent metal cation.

A preclinical evaluation of cytarabine prodrug nanofibers assembled from cytarabine-lauric acid conjugate toward solid tumors.

Cytarabine (Ara-C) has become cornerstones for the treatment of hatmatological malignancies for several decades; however, it still faces serious challenges in clinical applications due to its side effects such as hand foot syndrome (HFS) and stomatitis. Therefore, considerable researchers have devoted to looking for the new derivative with desirable activity and low toxicity. A new prodrug based on the conjugation of cytarabine with lauric acid (LA-Ara) was synthesized in our group, and it could self-assemble into nanofibers (NFs) in aqueous solution with high drug loading (57 wt%). The lauric acid moiety protects NH2 group of from the enzymatic attachment and simultaneously raises the lipophilicity of Ara-C, thus obviously prolongs its plasma half-life. The oil/water partition coefficient (lg P) and the permeability of cell membrane of LA-Ara were obviously increased compared with Ara-C. Furthermore, the in vitro gastrointestinal stability results indicated the prodrug was suitable to be administrated orally. In the current study, the in vitro cytotoxicity and in vivo anti breast cancer experimental results indicate LA-Ara markedly improved antitumor activity compared with free Ara-C. The favorable safety evaluations elucidated its potentiality for oral alternative treatment to Ara-C. Importantly, LA-Ara can effectively decrease the incidence of toxic effects (HFS and stomatitis) of Ara-C, thereby exhibiting favorable skin safety profile. Overall, these results indicated the LA-Ara would be an excellent candidate for further clinical investigation and simultaneously highlight the prospects of Ara-C prodrug strategies in solid tumors therapy.

Visual Recognition and Removal of C2H2 from C2H4/C2H2 Mixtures by a CuI-MOF.

A CuI-MOF was found to be a highly selective visual sensor for recognizing C2H2. Gas chromatography studies indicated that it can be used to effectively remove minor amounts of C2H2 from C2H4/C2H2 mixtures (98:2) and produce highly pure C2H4 (nearly 100%).

Vanadium-Doped WS2 Nanosheets Grown on Carbon Cloth as a Highly Efficient Electrocatalyst for the Hydrogen Evolution Reaction.

Two-dimensional transition-metal dichalcogenides have been widely studied as electrocatalysts for the hydrogen evolution reaction (HER). However, limited active sites and poor conductivity hinder their application. To solve these disadvantages, heteroatom doping has attracted wide attention because it can not only increase the active sites but also affect the intrinsic catalytic properties of the electrocatalyst. Herein, we grew vanadium-doped WS2 nanosheets on carbon cloth (V-WS2 /CC) as an electrocatalyst for HER under acidic and alkaline conditions. With a proper vanadium doping concentration, the electrochemical surface areas of V0.065 -WS2 /CC were 9.6 and 2.6 times as large as that of pure WS2 electrocatalyst under acidic and alkaline conditions, respectively. In addition, the charge-transfer resistance also decreased with moderate vanadium doping. Based on this, the synthesized vanadium-doped WS2 nanosheets exhibited good stability with high HER catalytic activity and could reach a current density of 10 mA cm-2 at overpotentials of 148 and 134 mV in 0.5 m H2 SO4 and 1 m KOH, respectively. The corresponding Tafel slopes were 71 and 85 mV dec-1 . Therefore, our synthesized vanadium-doped WS2 nanosheets can be a promising electrocatalyst for the production of hydrogen over a wide pH range.

Synthesis of a trisaccharide repeating unit of the O-antigen from Burkholderia cenocepacia and its dimer.

The trisaccharide repeating unit of an O-antigen derived from Burkholderia cenocepacia and its dimer, i.e., α-L-Rhap-(1 â†’ 3)-α-D-GalpNAc-(1 â†’ 3)-ß-D-GalpNAc-O(CH2)3N3 (1) and α-L-Rhap-(1 â†’ 3)-α-D-GalpNAc-(1 â†’ 3)-ß-D-GalpNAc-(1 â†’ 4)-α-L-Rhap-(1 â†’ 3)-α-D-GalpNAc-(1 â†’ 3)-ß-D-GalpNAc-O(CH2)3N3 (2), respectively, were synthesized via a highly convergent strategy. Glycosylation of galactosaminyl acceptor 4 with galactosaminyl trichloroacetimidate donor 5 was followed by condensation of resulting disaccharide acceptor 12 with rhamnosyl imidate donor 6 to furnish stereoselectively trisaccharyl thioglycoside 3, which was used as a key and common glycosyl donor for the construction of both 1 and 2. Title molecule 1 was prepared by glycosylation of 3-azidopropanol with 3 and subsequently global deprotection, whereas coupling reaction of 3 with a trisaccharide acceptor 21 containing an 2,3-O-position acetonide-modified rhamnose residue, followed by global deprotection, generated the dimer 2 in a convergent [3 + 3] manner.