Reactivity of oxygen radical anions bound to scandia nanoparticles in the gas phase: C-H bond activation.

The activation of C-H bonds in alkanes is currently a hot research topic in chemistry. The atomic oxygen radical anion (O(-·)) is an important species in C-H activation. The mechanistic details of C-H activation by O(-·) radicals can be well understood by studying the reactions between O(-·) containing transition metal oxide clusters and alkanes. Here the reactivity of scandium oxide cluster anions toward n-butane was studied by using a high-resolution time-of-flight mass spectrometer coupled with a fast flow reactor. Hydrogen atom abstraction (HAA) from n-butane by (Sc2O3)(N)O(-) (N=1-18) clusters was observed. The reactivity of (Sc2O3)(N)O(-) (N=1-18) clusters is significantly sizedependent and the highest reactivity was observed for N=4 (Sc8O13(-)) and 12 (Sc24O37(-)). Larger (Sc2O3)(N)O(-) clusters generally have higher reactivity than the smaller ones. Density functional theory calculations were performed to interpret the reactivity of (Sc2O3)(N)O(-) (N=1-5) clusters, which were found to contain the O(-·) radicals as the active sites. The local charge environment around the O(-·) radicals was demonstrated to control the experimentally observed size-dependent reactivity. This work is among the first to report HAA reactivity of cluster anions with dimensions up to nanosize toward alkane molecules. The anionic O(-·) containing scandium oxide clusters are found to be more reactive than the corresponding cationic ones in the C-H bond activation.

[Breviscapine listed on progress of new varieties and dosage form research].

Breviscapine, a flavone glucuronide, is a cardiovascular medicine extracted from a Chinese herb Erigeron breviscapinus. Modern pharmacological research shows breviscapine has a therapeutic effect on cardiovascular diseases such as cerebral thrombus,cerebral ischemia hemiparesis and platelet aggregation et al. However, its poor water solubility and low bioavailability in vivo severely restrict the clinical application. In this article, we reviewed the marketing preparations of breviscapine and its research progress on the new dosage forms.

Outer membrane protein OmpW of Escherichia coli is required for resistance to phagocytosis.

Eight-stranded ß-barrel outer membrane proteins can confer bacterial virulence via resistance to host innate defenses. This resistance function of OmpW, which was recently identified as an eight-stranded ß-barrel protein, was investigated in this study. Our results demonstrated that upregulation of OmpW correlated with increased bacterial survival during phagocytosis. Bacterial mutants harboring a deletion of ompW exhibited a significantly increased phagocytosis rate. Both observations suggest that the OmpW protein protects bacteria against host phagocytosis. In addition, expression of ompW is regulated by iron, which implies that the resistance provided by OmpW may be an important factor in iron-related infectious diseases. Furthermore, OmpW has been identified as a protective antigen that protects mice against bacterial infection and is therefore a promising target for vaccine development against infectious diseases.

C-H bond activation by aluminum oxide cluster anions, an experimental and theoretical study.

Aluminum oxide cluster anions are produced by laser ablation and reacted with n-butane in a fast flow reactor. A reflectron time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Aluminum oxide clusters Al2O4,6⁻ and Al3O7⁻ can react with n-C4H10 to produce Al2O4,6H⁻ and Al3O7⁻, respectively, while cluster Al3O6⁻ reacts with n-C4H10 to produce both the Al3O6H⁻ and Al3O6H2⁻. The theoretical calculations are performed to study the structures and bonding properties of clusters Al2O4,6⁻ and Al3O6,7⁻ as well as the reaction mechanism of Al2O4⁻ + n-C4H10. The calculated results show that the mononuclear oxygen-centred radicals (O⁻˙) on Al2O4,6⁻ and Al3O7⁻, and oxygen-centred biradical on Al3O6⁻ are the active sites responsible for the observed hydrogen atom abstraction reactivity. Furthermore, mechanism investigation of the O⁻˙ generation in Al3O7⁻ upon O2 molecule adsorption on un-reactive Al3O5⁻ is performed by theoretical calculations.

Structures and reactivity of oxygen-rich scandium cluster anions ScO(3-5)-.

Oxygen-rich scandium cluster anions ScO(3-5)(-) are prepared by laser ablation and allowed to react with n-butane in a fast-flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. The ScO(3)(-) and ScO(4)(-) clusters can react with n-butane to produce ScO(3)H(-), ScO(3)H(2)(-), and ScO(4)H(-), while the more oxygen-rich cluster ScO(5)(-) is inert. The experiment suggests that unreactive cluster isomers of ScO(3)(-) and ScO(4)(-) are also present in the cluster source. Density functional theory and ab initio methods are used to calculate the structures and reaction mechanisms of the clusters. The theoretical results indicate that the unreactive and reactive cluster isomers of ScO(3,4)(-) contain peroxides (O(2)(2-)) and oxygen-centered radicals (O(.-)), respectively. The mechanisms and energetics for conversion of unreactive O(2)(2-) to reactive O(.-) species are also theoretically studied.

[Value of monitoring oxygen metabolism in multiple organ dysfunction syndrome after severe trauma].

OBJECTIVE: To study changes in oxygen metabolism and evaluate metabolic status in tissue and cell after severe trauma, and to investigate value of monitoring oxygen metabolism in the course of development of multiple organ dysfunction syndrome (MODS) in trauma between patients. METHODS: The data of 146 patients with severe trauma in Tongji Hospital were collected. The variables pertaining to oxygen metabolism were analyzed, and the data were compared between patients with risky trauma and those with severe trauma, between patients complicated with MODS and non--MODS (NMODS), and between survivors and nonsurvivors. With patients with minor trauma as control, the data were analyzed according to injury severity score (ISS), revised trauma score (RTS), acute physiology and chronic health evaluation II (APACHE II), trauma and injury severity score (TRISS(RTS)) methods for trauma and outcome study of probability of survival (Ps). RESULTS: Oxygen metabolism abnormality was found after trauma, and it was correlated with ISS, RTS, injured organ or region and number of injured organs, shock, systemic inflammatory response syndrome (SIRS) and respiratory complications. It was more intense in the patients with MODS. There was marked difference in the ratio of change in oxygen metabolism between MODS and NMODS groups. Oxygen deficiency metabolic variables tended to deteriorate in the non survival group. More marked changes in metabolic variables indicated severer organ dysfunction, reaching their peak values before death. CONCLUSION: Changes in level of oxygen metabolism might be closely correlated with development of MODS in trauma patients. Dynamic monitorings of metabolic status of tissue and cell are valuable in predicting the development of MODS after severe trauma.