Aerobic Oxidation of Formaldehyde Catalyzed by Polyvanadotungstates

Three tetra-<i>n</i>-butylammonium (TBA) salts of polyvanadotungstates, [<i>n</i>-Bu₄N]₆[PW₉V₃O₄₀] (<b>PW</b>_<b>9</b><b>V</b>_<b>3</b>), [<i>n</i>-Bu₄N]₅H₂PW₈V₄O₄₀ (<b>PW</b>_<b>8</b><b>V</b>_<b>4</b>), and [<i>n</i>-Bu₄N]₄H₅PW₆V₆O₄₀·20H₂O (<b>PW</b>_<b>6</b><b>V</b>_<b>6</b>), have been synthesized and shown to be effective catalysts for the aerobic oxidation of formaldehyde to formic acid under ambient conditions. These complexes, characterized by elemental analysis, Fourier transform infrared spectroscopy, UV–vis spectroscopy, and thermogravimetric analysis, exhibit a catalytic activity for this reaction comparable to those of other polyoxometalates. Importantly, they are more effective in the presence of water than the metal oxide-supported Pt and/or Au nanoparticles traditionally used as catalysts for formaldehyde oxidation in the gas phase. The polyvanadotungstate-catalyzed oxidation reactions are first-order in formaldehyde, parabolic-order (slow, fast, and slow again) in catalyst, and zero-order in O₂. Under optimized conditions, a turnover number of ∼57 has been obtained. These catalysts can be recycled and reused without a significant loss of catalytic activity

Additional file 1 of Large-scale analysis of protein crotonylation reveals its diverse functions in Pinellia ternata

Additional file 1: Fig. S1. The flow chart of lysine crotonylation analysis (a), Distribution of Kcr-modified proteins based on the number of crotonylation sites in a protein (b). The analysis was performed based on 2106 crotonylated sites matched on 1006 proteins overlapping in three independent tests

Additional file 2 of Large-scale analysis of protein crotonylation reveals its diverse functions in Pinellia ternata

Additional file 2: Supplementary Table S1. Crotonylated sites of proteins in the leaves of P. ternata

DNA Cryogels with Anisotropic Mechanical and Responsive Properties for Specific Cell Capture and Release

Due to their programmable stimuli-responsiveness, excellent biocompatibility, and water-rich and soft structures similar to biological tissues, smart DNA hydrogels hold great promise for biosensing and biomedical applications. However, most DNA hydrogels developed to date are composed of randomly oriented and isotropic polymer networks, and the resulting slow response to biotargets and lack of anisotropic properties similar to those of biological tissues have limited their extensive applications. Herein, anisotropic DNA hydrogels consisting of unidirectional void channels internally oriented up to macroscopic length scales were constructed by a directional cryopolymerization method, as exemplified by a DNA-incorporated covalently cross-linked DNA cryogel and a DNA duplex structure noncovalently cross-linked DNA cryogel. Results showed that the formation of unidirectional channels significantly improved the responsiveness of the gel matrix to biomacromolecular substances and further endowed the DNA cryogels with anisotropic properties, including anisotropic mechanical properties, anisotropic swelling/shrinking behaviors, and anisotropic responsiveness to specific biotargets. Moreover, the abundant oriented and long macroporous channels in the gel matrix facilitated the migration of cells, and through the introduction of aptamer structures and thermosensitive polymers, an anisotropic DNA cryogel-based platform was further constructed to achieve the highly efficient capture and release of specific cells. These anisotropic DNA hydrogels may provide new opportunities for the development of anisotropic separation and biosensing systems

Additional file 4 of Large-scale analysis of protein crotonylation reveals its diverse functions in Pinellia ternata

Additional file 4: Supplementary Table S3. GO enrichment analysis of crotonylated proteins in the leaves of P. ternata

Self-Assembly of Luminescent Ag Nanocluster-Functionalized Nanowires

Two different methods to self-assemble red- or yellow-luminescent nucleic acids-stabilized Ag nanoclusters (NCs) nanowires are presented. By one method, the autonomous hybridization–polymerization process between two nucleic acids leads to polymer chains consisting of sequence-specific loops for the stabilization of the red- or yellow-emitting Ag NCs. By the other method, the nucleic acid-triggered hybridization chain reaction (HCR) involving the cross-opening of two functional hairpins leads to sequence-specific DNA loops and a nucleic acid scaffold that stabilize the respective red- or yellow-emitting Ag NCs. The micrometer-long luminescent Ag NC-functionalized nanowires are imaged by AFM and confocal microscopy

Probing Biocatalytic Transformations with Luminescent DNA/Silver Nanoclusters

DNA-stabilized Ag nanoclusters, AgNCs, act as fluorescent labels for probing enzyme activities and their substrates. The effective quenching of AgNCs by H₂O₂ enables the probing of H₂O₂-generating oxidases. This is demonstrated by following the glucose oxidase-stimulated oxidation of glucose through the enzyme-catalyzed formation of H₂O₂. Similarly, the effective quenching of the AgNCs by quinones enabled the detection of tyrosinase through the biocatalyzed oxidation of tyrosine, dopamine, or tyramine to the respective quinone products. The sensitive probing of biocatalytic processes by the AgNCs was further implemented to follow bienzyme catalytic cascades involving alkaline phosphatase/tyrosinase and acetylcholine esterase/choline oxidase. The characterization of the alkaline phosphatase/tyrosinase cascade enabled the ultrasensitive detection of alkaline phosphatase (5 × 10^–5 units/mL) and the detection of <i>o</i>-phospho-l-tyrosine that is an important intracellular promoter and control growth factor

Multitriggered Shape-Memory Acrylamide–DNA Hydrogels

Acrylamide–acrylamide nucleic acids are cross-linked by two cooperative functional motives to form shaped acrylamide–DNA hydrogels. One of the cross-linking motives responds to an external trigger, leading to the dissociation of one of the stimuli-responsive bridges, and to the transition of the stiff shaped hydrogels into soft shapeless states, where the residual bridging units, due to the chains entanglement, provide an intrinsic memory for the reshaping of the hydrogels. Subjecting the shapeless states to counter stimuli restores the dissociated bridges, and regenerates the original shape of the hydrogels. By the cyclic dissociation and reassembly of the stimuli-responsive bridges, the reversible switchable transitions of the hydrogels between stiff shaped hydrogel structures and soft shapeless states are demonstrated. Shaped hydrogels bridged by K⁺-stabilized G-quadruplexes/duplex units, by i-motif/duplex units, or by two different duplex bridges are described. The cyclic transitions of the hydrogels between shaped and shapeless states are stimulated, in the presence of appropriate triggers and counter triggers (K⁺ ion/crown ether; pH = 5.0/8.0; fuel/antifuel strands). The shape-memory hydrogels are integrated into shaped two-hydrogel or three-hydrogel hybrid structures. The cyclic programmed transitions of selective domains of the hybrid structures between shaped hydrogel and shapeless states are demonstrated. The possible applications of the shape-memory hydrogels for sensing, inscription of information, and controlled release of loads are discussed

Integration of Switchable DNA-Based Hydrogels with Surfaces by the Hybridization Chain Reaction

A novel method to assemble acrylamide/acrydite DNA copolymer hydrogels on surfaces, specifically gold-coated surfaces, is introduced. The method involves the synthesis of two different copolymer chains consisting of hairpin A, H_A, modified acrylamide copolymer and hairpin B, H_B, acrylamide copolymer. In the presence of a nucleic acid promoter monolayer associated with the surface, the hybridization chain reaction between the two hairpin-modified polymer chains is initiated, giving rise to the cross-opening of hairpins H_A and H_B and the formation of a cross-linked hydrogel on the surface. By the cofunctionalization of the H_A- and H_B-modified polymer chains with G-rich DNA tethers that include the G-quadruplex subunits, hydrogels of switchable stiffness are generated. In the presence of K⁺-ions, the hydrogel associated with the surface is cooperatively cross-linked by duplex units of H_A and H_B, and K⁺-ion-stabilized G-quadruplex units, giving rise to a stiff hydrogel. The 18-crown-6-ether-stimulated elimination of the K⁺-ions dissociates the bridging G-quadruplex units, resulting in a hydrogel of reduced stiffness. The duplex/G-quadruplex cooperatively stabilized hydrogel associated with the surface reveals switchable electrocatalytic properties. The incorporation of hemin into the G-quadruplex units electrocatalyzes the reduction of H₂O₂. The 18-crown-6-ether stimulated dissociation of the hemin/G-quadruplex bridging units leads to a catalytically inactive hydrogel

Syntheses, Structural Characterization, and Catalytic Properties of Di- and Trinickel Polyoxometalates

The syntheses, structural characterization, and catalytic properties of two different nickel-containing polyoxometalates (POMs) are presented. The dinickel-containing sandwich-type POM [Ni₂(P₂W₁₅O₅₆)₂]^20– (<b>Ni</b>_<b>2</b>) exhibits an unusual αααα geometry. The trinickel-containing Wells–Dawson POM [Ni₃(OH)₃(H₂O)₃P₂W₁₆O₅₉]^9– (<b>Ni</b>_<b>3</b>) shows a unique structure where the [α-P₂W₁₅O₅₆]^12– ligand is capped by a triangular Ni₃O₁₃ unit and a WO₆ octahedron. <b>Ni</b>_<b>3</b> shows a high catalytic activity for visible-light-driven hydrogen evolution, while the activity for <b>Ni</b>_<b>2</b> is minimal. An analysis of the structures of multinickel-containing POMs and their hydrogen evolution activity is given