N2 cleavage by silylene and formation of H2Si(µ-N)2SiH2.

Fixation and functionalisation of N2 by main-group elements has remained scarce. Herein, we report a fixation and cleavage of the N ≡ N triple bond achieved in a dinitrogen (N2) matrix by the reaction of hydrogen and laser-ablated silicon atoms. The four-membered heterocycle H2Si(µ-N)2SiH2, the H2SiNN(H2) and HNSiNH complexes are characterized by infrared spectroscopy in conjunction with quantum-chemical calculations. The synergistic interaction of the two SiH2 moieties with N2 results in the formation of final product H2Si(µ-N)2SiH2, and theoretical calculations reveal the donation of electron density of Si to π* antibonding orbitals and the removal of electron density from the π bonding orbitals of N2, leading to cleave the non-polar and strong NN triple bond.

Effect of sublethal dose of chloramphenicol on biofilm formation and virulence in Vibrio parahaemolyticus.

Vibrio parahaemolyticus isolates are generally very sensitive to chloramphenicol. However, it is usually necessary to transfer a plasmid carrying a chloramphenicol resistance gene into V. parahaemolyticus to investigate the function of a specific gene, and the effects of chloramphenicol on bacterial physiology have not been investigated. In this work, the effects of sublethal dose of chloramphenicol on V. parahaemolyticus were investigated by combined utilization of various phenotypic assays and RNA sequencing (RNA-seq). The results showed that the growth rate, biofilm formation capcity, c-di-GMP synthesis, motility, cytoxicity and adherence activity of V. parahaemolyticus were remarkably downregulated by the sublethal dose of chloramphenicol. The RNA-seq data revealed that the expression levels of 650 genes were significantly differentially expressed in the response to chloramphenicol stress, including antibiotic resistance genes, major virulence genes, biofilm-associated genes and putative regulatory genes. Majority of genes involved in the synthesis of polar flagellum, exopolysaccharide (EPS), mannose-sensitive haemagglutinin type IV pilus (MSHA), type III secretion systems (T3SS1 and T3SS2) and type VI secretion system 2 (T6SS2) were downregulated by the sublethal dose of chloramphenicol. Five putative c-di-GMP metabolism genes were significantly differentially expressed, which may be the reason for the decrease in intracellular c-di-GMP levels in the response of chloramphenicol stress. In addition, 23 genes encoding putative regulators were also significantly differentially expressed, suggesting that these regulators may be involved in the resistance of V. parahaemolyticus to chloramphenicol stress. This work helps us to understand how chloramphenicol effect on the physiology of V. parahaemolyticus.

Complex with Linear B-B-B Skeleton Trapped in Dinitrogen Matrix: Matrix Infrared Spectra and Quantum Chemical Calculations.

The neutral (NN)-B-B-B-(N2) complex has been trapped in low-temperature dinitrogen matrix and identified by isotopic substitution and theoretical frequency calculations. The linear B-B-B skeleton is stabilized by two inequivalent N2, namely, one end-on and other side-on N2. The structure of linear B-B-B skeleton illustrates much difference from previously reported triangle configuration of B3 clusters. Frontier orbital analysis demonstrates that the σ orbital of end-on NN and the π-bonding orbital of side-on N2 acts as the donor orbital. π bonding character across B-B-B skeleton donates to the antibonding π* orbital of end-on NN and out of phase the B-B-B features π back-donation to antibonding π* orbital of side-on N2. The combination of strong σ-donating capacity coupled with a greater ability for accepting π-back-donation of the N2 ligand leads to the formation of (NN)-B-B-B-(N2) complex with linear B-B-B skeleton. In addition, complexes of (NN)B(NN), (NN)BB(NN), and (NN)B4(NN) have been identified in our experiments.

F2BMF (M = B and Al) Molecules: A Matrix Infrared Spectra and Theoretical Calculations Investigation.

Reactions of laser-ablated B and Al atoms with BF3 have been explored in the 4 K excess neon through the matrix isolation infrared spectrum, isotopic substitutions and quantum chemical calculations. The inserted complexes F2BMF (M = B, Al) were identified by anti-symmetric and symmetric stretching modes of F-B-F, and the F-11B-F stretch modes are at 1336.9 and 1202.4 cm-1 for F211B11BF and at 1281.5 and 1180.8 cm-1 for F211BAlF. The CASSCF analysis, EDA-NOCV calculation and the theory of atoms-in-molecules (AIM) are applied to investigate the bonding characters of F2BBF and F2BAlF molecules. The bonding difference between boron and aluminum complexes reveals interesting chemistries, and the FB species stabilization by a main group atom was first observed in this article.

Beryllium Dimer Reactions with Acetonitrile: Formation of Strong Be-Be Bonds.

Laser ablated Be atoms have been reacted with acetonitrile molecules in 4 K solid neon matrix. The diberyllium products BeBeNCCH3 and CNBeBeCH3 have been identified by D and 13C isotopic substitutions and quantum chemical calculations. The stabilization of the diberyllium species is rationalized from the formation of the real Be-Be single bonds with bond distances as 2.077 and 2.058 Å and binding energies as -27.1 and -77.2 kcal/mol calculated at CCSD (T)/aug-cc-pVTZ level of theory for BeBeNCCH3 and CNBeBeCH3, respectively. EDA-NOCV analysis described the interaction between Be2 and NC···CH3 fragments as Lewis "acid-base" interactions. In the complexes, the Be2 moiety carries positive charges which transfer from antibonding orbital of Be2 to the bonding fragments significantly strengthen the Be-Be bonds that are corroborated by AIM, LOL and NBO analyses. In addition, mono beryllium products BeNCCH3, CNBeCH3, HBeCH2CN and HBeNCCH2 have also been observed in our experiments.

[Characteristics of acupoint application for the sub-healthy condition treated with ancient and modern acupuncture based on data mining exploration].

The acupoint selection was retrieved from the ancient and modern literature on the treatment of sub-healthy condition with acupuncture. The law of acupoint application was analyzed so as to provide a certain reference to the determination of acupoint prescription in clinical acupuncture. The ancient literature was retrieved from Chinese basic ancient literature database. The modern literature was retrieved from Cochrane Library, Medline, PubMed, Ovid evidence-based medicine database, Chinese biomedical literature database, China journal full-text database, VIP journal full-text database and Wanfang database. The database mining software was adopted to explore the law of acupoint application in treatment of sub-healthy conditions with ancient and modern acupuncture. The acupoint use frequency, compatibility association rule, law for meridian use and the use regularity of specific points were analyzed. In the ancient treatment for sub-healthy condition, the top five commonly used acupoints are Shenmen (HT 7), Zhaohai (KI 6), Taibai (SP 3), Daling (PC 7) and Taixi (KI 3). The most commonly combined points are Zhangmen (LR 13), Taibai (SP 3) and Zhaohai (KI 6). The most commonly used meridians are the bladder meridian of foot-taiyang, kidney meridian of foot-shaoyin and liver meridian of foot-jueyin. The most commonly used specific points are the five-shu points. The most commonly used acupoints are located in the lower limbs. In the modern treatment, the top five commonly used acupoints are Zusanli (ST 36), Sanyinjiao (SP 6), Baihui (GV 20), Shenshu (BL 23) and Guanyuan (CV 4). The most commonly supplemented points are Hegu (LI 4) and Taichong (LR 3). The most commonly used meridians are the bladder meridian of foot-taiyang, the conception vessel and the governor vessel. The most commonly used specific points are the back-shu points. The most commonly used acupoints are located in the lower limbs. After the systematic comprehension of the relevant ancient and modern literature, the most commonly used acupoints are selected along the bladder meridian of foot-taiyang, and the most commonly used specific points are the back-shu points, the five-shu points and the front-mu-points. the acupoints are mostly located in the lower limbs.