Real-time imaging of sulfhydryl single-stranded DNA aggregation.

The structure and functionality of biomacromolecules are often regulated by chemical bonds, however, the regulation process and underlying mechanisms have not been well understood. Here, by using in situ liquid-phase transmission electron microscopy (LP-TEM), we explored the function of disulfide bonds during the self-assembly and structural evolution of sulfhydryl single-stranded DNA (SH-ssDNA). Sulfhydryl groups could induce self-assembly of SH-ssDNA into circular DNA containing disulfide bonds (SS-cirDNA). In addition, the disulfide bond interaction triggered the aggregation of two SS-cirDNA macromolecules along with significant structural changes. This visualization strategy provided structure information at nanometer resolution in real time and space, which could benefit future biomacromolecules research.

In Situ TEM Observation of Stagnant Liquid Layer Activation in Nanochannel.

The kinetics of mass transfer in a stagnant fluid layer next to an interface govern numerous dynamic reactions in diffusional micro/nanopores, such as catalysis, fuel cells, and chemical separation. However, the effect of the interplay between stagnant liquid and flowing fluid on the micro/nanoscopic mass transfer dynamics remains poorly understood. Here, by using liquid cell transmission electron microscopy (TEM), we directly tracked microfluid unit migration at the nanoscale. By tracking the trajectories, an unexpected mass transfer phenomenon in which fluid units in the stagnant liquid layer migrated two orders faster during gas-liquid interface updating was identified. Molecular dynamics (MD) simulations indicated that the chemical potential difference between nanoscale liquid layers led to convective flow, which greatly enhanced mass transfer on the surface. Our study opens up a pathway toward research on mass transfer in the surface liquid layers at high spatial and temporal resolutions.

Atomic Scale Tracking of Single Layer Oxide Formation: Self-Peeling and Phase Transition in Solution.

Liquid phase electron microscopy (TEM) is used to track the formation of In2 O3 ultrathin nanosheet in solution at atomic scale. This observation reveals that the formation of few atomic layer nanosheet goes through a complicated phase transition process from InCl3 . 3H2 O to In(OH)3 and then to In2 O3 . Interestingly, the intermediate InCl3 . 3H2 O nanosheet can grow via either layer by layer or the strain-driven enation growth from precursor solution. Moreover, in situ TEM results and density functional theory (DFT) calculations demonstrate that the oleylamine is responsible for the self-peeling process. These findings can provide atomic-level insight for the understanding of how 2D nanomaterial grows and transforms in solution.

Polysaccharide isolated from Auricularia auricular-judae (Bull.) prevents dextran sulfate sodium-induced colitis in mice through modulating the composition of the gut microbiota.

Inflammatory bowel disease (IBD) is a chronic intestinal disease, which was commonly found in westerners whereas is increasingly prevalent in Asia because of the changing eating habits. In previous research, we found that a water-soluble polysaccharide isolated from Auricularia auricular-judae (Bull.)-a kind of edible mushroom (Aap)-is composed of ß-1,3 glycosidic bonds, which is regarded as therapeutic or protective substance in enteritis. We therefore aimed to find the preventing effect of Aap on IBD. Here, we reported that pre-administration of Aap not only ameliorated weight loss, colon damage, and mucosal inflammation in colitis mice, but also prevented the damage of intestinal barrier by reducing the D-lactic acid and diamine oxidase level in plasma. Through high-throughput sequencing, we found that Aap changed gut microbiota composition. Furthermore, the preventing effect was transmissible via horizontal feces transfer from Aap-treated mice to normal mice. Our results indicated that oral administration of Aap is a promising protective substance of IBD. PRACTICAL APPLICATION: Our study proved that Auricularia auricula polysaccharide had substantial preventing effect on DSS-induced colitis in mice. This research might lay the theoretical foundation and technical support for the development of related functional foods. People could also enhance their gut immunity by eating Auricularia auricular in their daily life. Auricularia auricular as a highly nutritious agricultural product showed the broad significance in nutrition and food function.