On the dynamical nature of the active center in a single-site photocatalyst visualized by 4D ultrafast electron microscopy

Understanding the dynamical nature of the catalytic active site embedded in complex systems at the atomic level is critical to developing efficient photocatalytic materials. Here, we report, using 4D ultrafast electron microscopy, the spatiotemporal behaviors of titanium and oxygen in a titanosilicate catalytic material. The observed changes in Bragg diffraction intensity with time at the specific lattice planes, and with a tilted geometry, provide the relaxation pathway: the Ti⁴⁺=O²⁻ double bond transformation to a Ti³⁺−O¹⁻ single bond via the individual atomic displacements of the titanium and the apical oxygen. The dilation of the double bond is up to 0.8 Å and occurs on the femtosecond time scale. These findings suggest the direct catalytic involvement of the Ti³⁺−O¹⁻ local structure, the significance of nonthermal processes at the reactive site, and the efficient photo-induced electron transfer that plays a pivotal role in many photocatalytic reactions.Single-site catalysts of both the thermally and photoactivated kind now occupy a prominent place in industrial- and laboratory-scale heterogeneous catalysis (1–8). Among the most versatile of these are the ones consisting of coordinatively unsaturated transition metal ions (Ti, Cr, Fe, Mn…) that occupy substitutional sites in well-defined, three-dimensionally extended, open-structure silicates of the zeolite type. The well-known and most widely used are the 4- or 5-coordinated Ti(IV) ions accommodated within the crystalline phase of silica, silicalite (9–14).Titanosilicates, especially, are used extensively both industrially and in the laboratory for a wide range of chemo-, regio-, and shape-selective oxidations of organic compounds (15–18). These single-site heterogeneous photocatalysts are quite distinct from those typified by TiO₂, SrTiO₃, and other titaniferous photocatalysts where the Ti(IV) ions are in 6-coordination; and where, in interpreting the processes involved in harnessing solar radiation, electronic band structure considerations hold sway in preference to the localized states (see, e.g., refs. 19, 20). It has been demonstrated (16–18, 21, 22) that single-site, coordinatively unsaturated Ti(IV)-centered photocatalysts are especially useful in the aerial oxidation of environmental pollutants in the photodegradation of NO (to N₂ and O₂), of H₂O (to H₂ and O₂), and in the photocatalytic reduction of CO₂ to yield methanol. There is an exigent need to explore the precise nature of the electronic, temporal, and spatial changes accompanying the initial act of photoabsorption that sets in train the ensuing elementary chemical processes that are of vital environmental significance in, for example, the utilization of anthropogenic CO₂ as a chemical feedstock (23).Here, we report the use of 4D ultrafast electron microscopy (UEM) (24–26) to trace the spatiotemporal behavior of the Ti(IV) and O²⁻ ions at the photocatalytic active center in the structurally well-characterized titanosilicate Na₄Ti₂Si₈O₂₂·4H₂O, known as JDF-L1 (27–29). JDF stands for Jilin–Davy–Faraday, as the crystalline solid described here was discovered and characterized in joint work involving Jilin University (P. R. China) and the Davy–Faraday Laboratory at the Royal Institution of Great Britain. L1 stands for the first layered catalyst formed during that collaboration; 5-coordinated solids containing Ti(IV) ions are rare among the hundred or so titaniferous minerals, the prime example being fresnoite, Ba₂Ti₂Si₂O₈. We choose this photocatalyst with 5-coordinated Ti because of its unique bonding structure. Our approach entails monitoring, at femtosecond resolution, the changes in intensities and anisotropies of Bragg (electron) diffraction reflections in such a manner as to retrieve the change in valency and the time scales involved in both the formation of Ti³⁺−O¹⁻ bond and the relaxation of the energy back to the local structure of the Ti = O bond in JDF-L1. Through these diffraction studies, and the associated Debye–Waller effect and structural factors anisotropies, it is found that a Ti³⁺−O¹⁻ bond is formed on the femtosecond time scale; whereas, the back relaxation from the site to the structure occurs on a much longer time scale, permitting ample time for reactivity involving Ti³⁺−O¹⁻, and indicating the potential significance of nonthermal processes in the photocatalytic activity at the reactive site.     

Clearance of hepatitis B surface antigen (HBsAg) after surgical resection of hepatocellular carcinoma

The serum HBsAg in 4 chronic HBsAg carrier patients with hepatocellular carcinoma (HCC) cleared within 4-38 months after surgical resection of their hepatic tumors. Two patients developed anti-HBs. During the follow-up period from 21 to 28 months after HBsAg clearance, none of the patients regained positive serum HBsAg. Two patients who had had tissue HBsAg present, exclusively in the tumor, showed quick HBsAg clearance after resection. The other 2 patients had a delayed HBsAg clearance. One had tissue HBsAg in both the tumor and nontumoral liver. Only 1 patient had tissue HBsAg in the liver, but not in the tumor. During the same period of observation of 323 chronic HBsAg carriers, who had a variety of histologically-verified chronic liver diseases and were followed for more than 6 months, only 1 cleared the antigen. The spontaneous HBsAg clearance in our HBsAg carriers (1/323) was significantly lower than that (4/64) of HBsAg-positive HCC patients with tumor resection, P less than 0.004. The mechanisms of HBsAg clearance in HCC patients after surgical resection of tumors are discussed.     

Berberine Blocks the Relapse of Clostridium difficile Infection in C57BL/6 Mice after Standard Vancomycin Treatment

Vancomycin is a preferred antibiotic for treating Clostridium difficile infection (CDI) and has been associated with a rate of recurrence of CDI of as high as 20% in treated patients. Recent studies have suggested that berberine, an alternative medical therapy for gastroenteritis and diarrhea, exhibits several beneficial effects, including induction of anti-inflammatory responses and restoration of the intestinal barrier function. This study investigated the therapeutic effects of berberine on preventing CDI relapse and restoring the gut microbiota in a mouse model. Berberine was administered through gavage to C57BL/6 mice with established CDI-induced intestinal injury and colitis. The disease activity index (DAI), mean relative weight, histopathology scores, and levels of toxins A and B in fecal samples were measured. An Illumina sequencing-based analysis of 16S rRNA genes was used to determine the overall structural change in the microbiota in the mouse ileocecum. Berberine administration significantly promoted the restoration of the intestinal microbiota by inhibiting the expansion of members of the family Enterobacteriaceae and counteracting the side effects of vancomycin treatment. Therapy consisting of vancomycin and berberine combined prevented weight loss, improved the DAI and the histopathology scores, and effectively decreased the mortality rate. Berberine prevented CDIs from relapsing and significantly improved survival in the mouse model of CDI. Our data indicate that a combination of berberine and vancomycin is more effective than vancomycin alone for treating CDI. One of the possible mechanisms by which berberine prevents a CDI relapse is through modulation of the gut microbiota. Although this conclusion was generated in the case of the mouse model, use of the combination of vancomycin and berberine and represent a novel therapeutic approach targeting CDI.     

Kallistatin Ameliorates Influenza Virus Pathogenesis by Inhibition of Kallikrein-Related Peptidase 1-Mediated Cleavage of Viral Hemagglutinin

Proteolytic cleavage of the hemagglutinin (HA) of influenza virus by host trypsin-like proteases is required for viral infectivity. Some serine proteases are capable of cleaving influenza virus HA, whereas some serine protease inhibitors (serpins) inhibit the HA cleavage in various cell types. Kallikrein-related peptidase 1 (KLK1, also known as tissue kallikrein) is a widely distributed serine protease. Kallistatin, a serpin synthesized mainly in the liver and rapidly secreted into the circulation, forms complexes with KLK1 and inhibits its activity. Here, we investigated the roles of KLK1 and kallistatin in influenza virus infection. We show that the levels of KLK1 increased, whereas those of kallistatin decreased, in the lungs of mice during influenza virus infection. KLK1 cleaved H1, H2, and H3 HA molecules and consequently enhanced viral production. In contrast, kallistatin inhibited KLK1-mediated HA cleavage and reduced viral production. Cells transduced with the kallistatin gene secreted kallistatin extracellularly, which rendered them more resistant to influenza virus infection. Furthermore, lentivirus-mediated kallistatin gene delivery protected mice against lethal influenza virus challenge by reducing the viral load, inflammation, and injury in the lung. Taking the data together, we determined that KLK1 and kallistatin contribute to the pathogenesis of influenza virus by affecting the cleavage of the HA peptide and inflammatory responses. This study provides a proof of principle for the potential therapeutic application of kallistatin or other KLK1 inhibitors for influenza. Since proteolytic activation also enhances the infectivity of some other viruses, kallistatin and other kallikrein inhibitors may be explored as antiviral agents against these viruses.     

心脏瓣膜置换同期行双极射频消融术治疗房颤的临床疗效

目的探讨心脏瓣膜置换同期行双极射频消融术(BRFA)治疗心房纤颤(AF)的临床疗效及安全性。方法回顾性分析2011年1月至2012年12月在瓣膜置换术同期行BRFA治疗的90例AF患者临床资料,患者在全身麻醉开胸直视体外循环下行瓣膜置换术及BRFA。术后随访患者心脏彩色超声、心电图等指标,分析比较其疗效。结果患者动脉阻断时间为65~120 min,平均(75.5±24.5)min,体外循环时间为45~200 min,平均(112.5±30.8)min;BRFA时间为13~28min,平均(21.5±7.5)min。随访结果表明91.11%患者术后3个月维持窦性心律,术后12个月左心房、左心室径线较术前明显减小,左心室射血分数较术前明显增高,差异有统计学意义(P0.05);同时房颤持续时间、术前左房径线及左室径线对手术成功有影响。结论心脏瓣膜置换术同期行BRFA治疗AF安全、简便且效果良好,值得临床推广应用。     

手术大量输血后患者电解质及凝血功能的变化

目的探讨手术大量输血后对患者机体血清电解质和凝血功能的变化。方法对25例大量输血患者输血中,输血后血清电解质和凝血功能进行检测分析。结果术中输入小于1 000mL血液制品后,凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)、凝血酶时间(TT)和K+、Na+、Cl-、Ca2+均无明显改变(P0.05),但术后输入3 000mL以上血液制品,PT、APTT、TT时间明显延长(P0.01),同时纤维蛋白原(FIB)水平明显下降,K+、Ca2+下降明显(P0.01)。结论患者大量输血后极易出现低钾和低钙血症及凝血功能紊乱,手术时应动态监测各项指标,以防严重并发症的发生。     

1294例女性高危型人乳头瘤病毒基因分型结果回顾性分析

目的了解北京地区妇科门诊就诊女性高危型人乳头瘤病毒(HPV)的感染及其基因亚型分布情况,为该市今后防治人乳头瘤病毒感染和宫颈癌提供参考依据。方法回顾性分析2013年1月至2014年5月该院妇科门诊就诊的1 294例女性宫颈拭子的13种高危型HPV基因分型检测结果,比较不同基因型的流行病学特点。采用SPSS17.0对数据进行统计学分析。结果 1 294例妇科门诊就诊女性中,以58型、16型和52型HPV最为常见,检出率分别为10.5%、9.2%和8.2%。各年龄段就诊女性中,30~40岁的HPV感染率最高(39.9%),其次为40~50岁、大于或等于60岁,差异无统计学意义(P0.05)。结论该地区妇科门诊就诊女性高危型HPV感染率较高,应加强HPV筛查力度,为今后HPV相关疾病的防治提供基础依据。     

高迁移率族蛋白B1靶向治疗的研究进展

高迁移率族蛋白B1 (HMGB1)为重要炎性因子,其为无菌性炎症与感染相关炎症反应的重要调节者,在感染、炎症及免疫反应中发挥重要作用.HMGB1表达水平可反映机体炎症及组织损伤的严重程度,且与相关疾病的预后密切相关.以HMGB1为治疗靶点,有望为感染、自身免疫性疾病、缺血再灌注损伤(IRI)、移植物抗宿主病(GVHD)等疾病的治疗提供潜在新策略.