Reversible Regulation of Protein Binding Affinity by a DNA Machine

We report a DNA machine that can reversibly regulate target binding affinity on the basis of distance-dependent bivalent binding. It is a tweezer-like DNA machine that can tune the spatial distance between two ligands to construct or destroy the bivalent binding. The DNA machine can strongly bind to the target protein when the ligands are placed at an appropriate distance but releases the target when the bivalent binding is disrupted by enlargement of the distance between the ligands. This “capture–release” cycle could be repeatedly driven by single-stranded DNA without changing the ligands and target protein

Domain-Confined Multiple Collision Enhanced Catalytic Soot Combustion over a Fe₂O₃/TiO₂–Nanotube Array Catalyst Prepared by Light-Assisted Cyclic Magnetic Adsorption

The ordered TiO₂ nanotube array (NA)-supported ferric oxide nanoparticles with adjustable content and controllable particulate size were prepared through a facile light-assisted cyclic magnetic adsorption (LCMA) method. Multiple techniques such as SEM, TEM, EDX, XRD, EXAFS, XPS, UV–vis absorption, and TG were employed to study the structure and properties of the catalysts. The influencing factors upon soot combustion including the annealing temperature and loading of the active component in Fe₂O₃/TiO₂–NA were also investigated. An obvious confinement effect on the catalytic combustion of soot was observed for the ferric oxide nanoparticles anchored inside TiO₂ nanotubes. On the basis of the catalytic performance and characterization results, a novel domain-confined multiple collision enhanced soot combustion mechanism was proposed to account for the observed confinement effect. The design strategy for such nanotube array catalysts with domain-confined macroporous structure is meaningful and could be well-referenced for the development of other advanced soot combustion catalysts

DNA-Grafted Polypeptide Molecular Bottlebrush Prepared via Ring-Opening Polymerization and Click Chemistry

A new type of DNA grafted polypeptide molecular brush was synthesized via a combination of ring-opening polymerization (ROP) and click chemistry. This conjugation method provides an easy and efficient approach to obtain a hybrid DNA-grafted polypeptide molecular bottlebrush. The structure and assembly behaviors of this hybrid brush were investigated using electrophoresis, UV–vis spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). Hierarchical supramolecular assemblies can be obtained through hybridization of two kinds of polypeptide-<i>g</i>-DNA molecular bottlebrushes containing complementary DNA side chains. We further demonstrated that such polypeptide-<i>g</i>-DNA can be hybridized with ds-DNA and DNA-grafted gold nanoparticles to form a supermolecular bottlebrush and hybrid bottlebrush, respectively. In addition, DNA-polypeptide hydrogel can be prepared by hybridization of polypeptide-<i>g</i>-DNA with a linker-ds-DNA, which contains the complementary “sticky ends” to serve as cross-linkers

Synergistic Effect of Titanate-Anatase Heterostructure and Hydrogenation-Induced Surface Disorder on Photocatalytic Water Splitting

Black TiO₂ obtained by hydrogenation has attracted enormous attention due to its unusual photocatalytic activity. In this contribution, a novel photocatalyst containing both a titanate–anatase heterostructure and a surface disordered shell was in situ synthesized by using a one-step hydrogenation treatment of titanate nanowires at ambient pressure, which exhibited remarkably improved photocatalytic activity for water splitting under simulated solar light. The as-hydrogenated catalyst with a heterostructure and a surface disordered shell displayed a high hydrogen production rate of 216.5 μmol·h^–1, which is ∼20 times higher than the Pt-loaded titanate nanowires lacking of such unique structure. The in situ-generated heterostructure and hydrogenation-induced surface disorder can efficiently promote the separation and transfer of photoexcited electron–hole pairs, inhibiting the fast recombination of the generated charge carriers. A general synergistic effect of the heterostructure and the surface disordered shell on photocatalytic water splitting is revealed for the first time in this work, and the as-proposed photocatalyst design and preparation strategy could be widely extended to other composite photocatalytic systems used for solar energy conversion

Association of TLR4 and Treg in <i>Helicobacter pylori</i> Colonization and Inflammation in Mice

<div><p>The host immune response plays an important role in the pathogenesis of <i>Helicobacter pylori</i> infection. The aim of this study was to clarify the immune pathogenic mechanism of <i>Helicobacter pylori</i> infection via TLR signaling and gastric mucosal Treg cells in mice. To discover the underlying mechanism, we selectively blocked the TLR signaling pathway and subpopulations of regulatory T cells in the gastric mucosa of mice, and examined the consequences on <i>H</i>. <i>pylori</i> infection and inflammatory response as measured by MyD88, NF-κB p65, and Foxp3 protein expression levels and the levels of Th1, Th17 and Th2 cytokines in the gastric mucosa. We determined that blocking TLR4 signaling in <i>H</i>. <i>pylori</i> infected mice decreased the numbers of Th1 and Th17 Treg cells compared to controls (P < 0.001–0.05), depressed the immune response as measured by inflammatory grade (P < 0.05), and enhanced <i>H</i>. <i>pylori</i> colonization (P < 0.05). In contrast, blocking CD25 had the opposite effects, wherein the Th1 and Th17 cell numbers were increased (P < 0.001–0.05), immune response was enhanced (P < 0.05), and <i>H</i>. <i>pylori</i> colonization was inhibited (P < 0.05) compared to the non-blocked group. In both blocked groups, the Th2 cytokine IL-4 remained unchanged, although IL-10 in the CD25 blocked group was significantly decreased (P < 0.05). Furthermore, MyD88, NF-κB p65, and Foxp3 in the non-blocked group were significantly lower than those in the TLR4 blocked group (P < 0.05), but significantly higher than those of the CD25 blocked group (P < 0.05). Together, these results suggest that there might be an interaction between TLR signaling and Treg cells that is important for limiting <i>H</i>. <i>pylori</i> colonization and suppressing the inflammatory response of infected mice.</p></div

Effects of Structural Flexibility on the Kinetics of DNA Y‑Junction Assembly and Gelation

The kinetics of DNA assembly is determined not only by temperature but also by the flexibility of the DNA tiles. In this work, the flexibility effect was studied with a model system of Y-junctions, which contain single-stranded thymine (T) loops in the center. It was demonstrated that the incorporation of a loop with only one thymine prominently improved the assembly rate and tuned the final structure of the assembly, whereas the incorporation of a loop of two thymines exhibited the opposite effect. These observations could be explained by the conformation adjustment rate and the intermotif binding strength. Increasing DNA concentration hindered the conformational adjustment rate of DNA strands, leading to the formation of hydrogels in which the network was connected by ribbons. Therefore, the gel can be treated as a metastable state during the phase transition

Expression of Th1, Th17, and Th2 cytokines in the gastric mucosa after <i>H</i>. <i>pylori</i> infection.

<p>(A) The expression of Th1 and Th17 with TLR4 blocked; (B) The expression of Th1 and Th17 with CD25 blocked; (C) The expression of Th2 with TLR4 blocked; (D) The expression of Th2 with CD25 blocked. ^a<i>P</i> < 0.05–0.001 <i>vs</i>. the control or TLR4 blocked control groups; ^b<i>P</i> < 0.001–0.05 between TLR4 blocked <i>H</i>. <i>pylori</i> and <i>H</i>. <i>pylori</i> groups (Fig 3A); ^a<i>P</i> < 0.001 <i>vs</i>. the control and CD25 blocked control groups; ^b<i>P</i> < 0.001–0.05 between CD25 blocked <i>H</i>. <i>pylori</i> and <i>H</i>. <i>pylori</i> groups (Fig 3B). ^a<i>P</i> < 0.01 <i>vs</i>. control and TLR4 blocked control groups (Fig 3C); ^a<i>P</i> < 0.01–0.001 <i>vs</i>. control and CD25 blocked control groups; ^b<i>P</i> < 0.05 between CD25 blocked and non-blocked <i>H</i>. <i>pylori</i> groups (Fig 3D).</p

Grade of gastritis after <i>H</i>. <i>pylori</i> infection.

<p>(A) The grade of gastritis with TLR4 blocked; (B) The grade of gastritis with CD25 blocked; (C) HE staining of the gastric mucosa of the control group; (D) HE staining of the gastric mucosa of the <i>H</i>. <i>pylori</i> infection group; (E) HE staining of the gastric mucosa of the TLR4 blocked control group; (F) HE staining of the gastric mucosa of the TLR4 blocked <i>H</i>. <i>pylori</i> infection group; (G) HE staining of the gastric mucosa of the CD25 blocked control group; (H) HE staining of the gastric mucosa of the CD25 blocked <i>H</i>. <i>pylori</i> infection group. ^a<i>P</i> < 0.001 between <i>H</i>. <i>pylori</i> and control or TLR4 blocked control groups; ^b<i>P</i> < 0.01 between TLR4 blocked <i>H</i>. <i>pylori</i> and control or TLR4 blocked control groups; ^c<i>P</i> < 0.05 between <i>H</i>. <i>pylori</i> and TLR4 blocked <i>H</i>. <i>pylori</i> groups (Fig 2A). ^a<i>P</i> < 0.001 <i>vs</i>. control and CD25 blocked control groups; ^b<i>P</i> < 0.05 between <i>H</i>. <i>pylori</i> and CD25 blocked <i>H</i>. <i>pylori</i> groups (Fig 2B).</p

Western blot detection conditions for MyD88 and Foxp3.

<p>Western blot detection conditions for MyD88 and Foxp3.</p

Expression of MyD88 and Foxp3 in the gastric mucosa after <i>H</i>. <i>pylori</i> infection by western blot.

<p>(A) The expression of MyD88 and Foxp3 with TLR4 blocked; (B) The expression of MyD88 and Foxp3 with CD25 blocked; (C, D) The expression of MyD88 and Foxp3 by western blotting. ^a<i>P</i> < 0.001 <i>vs</i>. control and TLR4 blocked control groups; ^b<i>P</i> < 0.001–0.05 <i>vs</i>. control and TLR4 blocked control groups and the <i>H</i>. <i>pylori</i> group (Fig 5A). ^a<i>P</i> < 0.01–0.001 <i>vs</i>. control and CD25 blocked control groups; ^b<i>P</i> < 0.05 between CD25 blocked <i>H</i>. <i>pylori</i> and <i>H</i>. <i>pylori</i> groups (Fig 5B).</p