Trapping Metallic Oxide Clusters inside Fullerene Cages.

The sub-nanometer sized void inside a fullerene cage permits the accommodation of a single atom, atomic cluster, or even small molecule, resulting in the formation of endohedral fullerenes. Particularly, clusterfullerenes can be formed by encapsulating multiple metallic ions in most cases along with nonmetal ions (i.e., N3-, C22-, S2-, O2-) inside the fullerene cage. Such an association makes clusterfullerene more functional than empty fullerenes and conventional mono-metallofullerenes. To date, a variety of clusterfullerenes have been reported, including metal nitrides, carbides, oxides, sulfides, cyanides, and so on. Among them, oxide clusterfullerenes (OCFs) can contain variable oxide clusters (i.e., M4O2, M4O3, M3O, and M2O; M = Sc or other metal), yielding one of the most versatile families. Thus, OCFs may provide a more convenient platform for developing new functional molecules and for studying previously less-explored topics such as formation mechanisms of clusterfullerenes. In this Account, we review recent progress in the field of OCFs, including their synthesis, isolation, and structural and electrochemical studies as well as the preliminary exploration into their potential functions and applications. Thanks to the concrete crystallographic results of an OCF series, we can track the transition of endohedral cluster and fullerene cage. It is suggested that the configuration and internal dynamics of the oxide cluster are highly dependent on not only the cage size but also cage structure. On the other hand, based on the experimental observations, two competitive transformation pathways are established for the majority of OCFs, verifying the bottom-up or top-down formation mechanism. It is also found that the redox behaviors of OCFs are more or less comparable to their isoelectronic species with common cage structure and similar cluster geometry but varied greatly with the cluster variety (i.e., Sc2O vs Sc4O2-3). The mechanism behind such phenomena has been discussed. In addition, the potential of Dy-based OCFs as single molecular magnets (SMMs) is presented theoretically. Nevertheless, experimental advance remains to be achieved.

Ho2O@C84: Crystallographic Evidence Showing Linear Metallic Oxide Cluster Encapsulated in IPR Fullerene Cage of D2d(51591)-C84.

Fullerene C84 is the third-most-abundant species after C60 and C70. In the past decade, a variety of C84-based clusterfullerenes have been well-studied experimentally, which otherwise do not include oxide clusterfullerenes (OCFs). In this work, we report a comprehensive inspection of Ho2O@C84, including its mass, spectroscopic, crystallographic, electrochemical (EC), and density functional theory (DFT) studies. Importantly, crystallographic data reveal an IPR cage of D2d(51591)-C84 with a linear endohedral Ho-O-Ho cluster, indicating that the compression effect of the C84 cage is less pronounced compared to that of a smaller cage. The experimentally observed structure is confirmed by DFT computations, which also verify its superior stability. Further studies suggest that Ho2O@C84 has reduced EC and HOMO-LUMO gaps compared to those of empty species, again demonstrating the effect of cluster encapsulation.

Ho2O@C74: Ho2O Cluster Expands within a Small Non-IPR Fullerene Cage of C2(13333)-C74.

Steering the cluster configuration inside a fullerene cage has been one of most interesting topics in the field of fullerenes, since the physical property of a cluster fullerene may be modified accordingly. It has been well-recognized that the cluster configuration can be tuned via altering the cage size. Typically, the carbide cluster and the oxide cluster are experimentally seen to be curled up within a small fullerene cage whereas they are expanded in a large cage. In this work, a new oxide cluster fullerene Ho2O@ C2(13333)-C74 is prepared and isolated. The single-crystal X-ray diffraction (XRD) study reveals that the Ho2O cluster, however, expands within the small non-IPR cage of C2(13333)-C74 with a Ho-O-Ho angle of >170°, indicating that cluster configuration is highly related to the cage shape and cage structure as well. The DFT computation demonstrates that the cluster-to-cage electron-transfer obviously enhances the aromaticity of the motif containing the fused-pentagon pair and hence stabilizes the non-IPR cage of C2(13333)-C74. In addition, the electrochemical and magnetic properties of Ho2O@ C2(13333)-C74 are studied to further investigate the effect of endohedral Ho2O cluster.

Musca domestica Cecropin (Mdc) Alleviates Salmonella typhimurium-Induced Colonic Mucosal Barrier Impairment: Associating With Inflammatory and Oxidative Stress Response, Tight Junction as Well as Intestinal Flora.

Salmonella typhimurium, a Gram-negative food-borne pathogen, induces impairment in intestinal mucosal barrier function frequently. The injury is related to many factors such as inflammation, oxidative stress, tight junctions and flora changes in the host intestine. Musca domestica cecropin (Mdc), a novel antimicrobial peptide containing 40 amino acids, has potential antibacterial, anti-inflammatory, and immunological functions. It remains unclear exactly whether and how Mdc reduces colonic mucosal barrier damage caused by S. typhimurium. Twenty four 6-week-old male mice were divided into four groups: normal group, control group (S. typhimurium-challenged), Mdc group, and ceftriaxone sodium group (Cs group). HE staining and transmission electron microscopy (TEM) were performed to observe the morphology of the colon tissues. Bacterial load of S. typhimurium in colon, liver and spleen were determined by bacterial plate counting. Inflammatory factors were detected by enzyme linked immunosorbent assay (ELISA). Oxidative stress levels in the colon tissues were also analyzed. Immunofluorescence analysis, RT-PCR, and Western blot were carried out to examine the levels of tight junction and inflammatory proteins. The intestinal microbiota composition was assessed via 16s rDNA sequencing. We successfully built and evaluated an S. typhimurium-infection model in mice. Morphology and microcosmic change of the colon tissues confirmed the protective qualities of Mdc. Mdc could inhibit colonic inflammation and oxidative stress. Tight junctions were improved significantly after Mdc administration. Interestingly, Mdc ameliorated intestinal flora imbalance, which may be related to the improvement of tight junction. Our results shed a new light on protective effects and mechanism of the antimicrobial peptide Mdc on colonic mucosal barrier damage caused by S. typhimurium infection. Mdc is expected to be an important candidate for S. typhimurium infection treatment.

Oral administration of Grifola frondosa polysaccharides improves memory impairment in aged rats via antioxidant action.

SCOPE: Grifola frondosa is an edible/medicinal mushroom with great nutritional value and bioactivity. The present study was performed to evaluate the beneficial effect of polysaccharides isolated from Grifola frondosa on memory impairment in aged rats. METHODS AND RESULTS: 20-month-old rats were gavaged with Grifola frondosa polysaccharides (GFP) for 8 weeks. Morris Water Maze test revealed that GFP administration significantly improved memory impairment in aged rats. GFP supply was also found to attenuate age-associated changes of brain histology and ultrastructure observed by light microscopy and transmission electron microscopy. Moreover, the increase of total antioxidant capacity (T-AOC), glutathione peroxidase (GPx) activity, superoxide dismutase (SOD) activity, catalase (CAT) activity, as well as the decreased nitric oxide (NO) and malondialdehyde (MDA) levels, were consistent with the behavioral results. CONCLUSION: These findings indicated that oral administration of GFP could improve memory impairment via antioxidant action, and dietary supplementation with GFP may provide potential benefits on brain aging.

Production of bioactive liver-targeting interferon Mu-IFN-CSP by soluble prokaryotic expression.

A novel liver-targeting interferon (IFN-CSP) was successfully over-expressed in our previous work. The in vitro and in vivo investigation revealed that IFN-CSP has significant anti-hepatitis B virus (HBV) effect and liver-targeting capacity. However, due to the IFN-CSP tends to form inclusion bodies in recombinant Escherichia coli (E. coli), efficient production of the soluble liver-targeting interferon is a challenge. In view of biomedical application, novel strategies for efficiently expressing liver-targeting interferon and overcoming its poor solubility are necessary and important. In the present study, a modified mu-IFN-CSP was designed base on the amino acid mutant of the native IFN-CSP. Meanwhile, the coding sequence of mu-IFN-CSP was optimized for E. coli preferred codon and the induction conditions for expression were optimized by an orthogonal test. After amino acid mutant, codon optimization and induction conditions optimization, the solubility of Mu-IFN-CSP in E. coli was up to 98.4%. The structural comparison and molecular dynamic simulation showed that the Mu-IFN-CSP formed three structure changes and were more stable than the native IFN-CSP. Tissue sections binding assays revealed that Mu-IFN-CSP was also able to specific binding to liver. In vitro anti-HBV activity assays showed that the soluble Mu-IFN-CSP has improved anti-HBV effect in HepG2.2.15 cells compared to the native IFN-CSP. The present study reports for the first time that liver-targeting interferon Mu-IFN-CSP can be expressed as soluble form, and also contributes to further support its application as liver-targeting anti-HBV medicine.