Investigation of c ions formed by N‐terminally charged peptides upon collision‐induced dissociation

Peptide fragments such as b and y sequence ions generated upon low‐energy collision‐induced dissociation have been routinely used for tandem mass spectrometry (MS/MS)‐based peptide/protein identification. The underlying formation mechanisms have been studied extensively and described within the literature. As a result, the ‘mobile proton model’ and ‘pathways in competition model’ have been built to interpret a majority of peptide fragmentation behavior. However, unusual peptide fragments which involve unfamiliar fragmentation pathways or various rearrangement reactions occasionally appear in MS/MS spectra, resulting in confused MS/MS interpretations. In this work, a series of unfamiliar c ions are detected in MS/MS spectra of the model peptides having an N‐terminal Arg or deuterohemin group upon low‐energy collision‐induced dissociation process. Both the protonated Arg and deuterohemin group play an important role in retention of a positive charge at the N‐terminus that is remote from the cleavage sites. According to previous reports and our studies involving amino acid substitutions and hydrogen–deuterium exchange, we propose a McLafferty‐type rearrangement via charge‐remote fragmentation as the potential mechanism to explain the formation of c ions from precursor peptide ions or unconventional b ions. Density functional theory calculations are also employed in order to elucidate the proposed fragmentation mechanisms. Copyright © 2016 John Wiley & Sons, Ltd.     

Giant Hollow Heterometallic Polyoxoniobates with Sodalite‐Type Lanthanide–Tungsten–Oxide Cages: Discrete Nanoclusters and Extended Frameworks

The first series of niobium–tungsten–lanthanide (Nb‐W‐Ln) heterometallic polyoxometalates {Ln₁₂W₁₂O₃₆(H₂O)₂₄(Nb₆O₁₉)₁₂} (Ln=Y, La, Sm, Eu, Yb) have been obtained, which are comprised of giant cluster‐in‐cluster‐like ({Ln₁₂W₁₂}‐in‐{Nb₇₂}) structures built from 12 hexaniobate {Nb₆O₁₉} clusters gathered together by a rare 24‐nuclearity sodalite‐type heterometal–oxide cage {Ln₁₂W₁₂O₃₆(H₂O)₂₄}. The Nb‐W‐Ln clusters present the largest multi‐metal polyoxoniobates and a series of rare high‐nuclearity 4d‐5d‐4f multicomponent clusters. Furthermore, the giant Nb‐W‐Ln clusters may be isolated as discrete inorganic alkali salts and can be used as building blocks to form high‐dimensional inorganic–organic hybrid frameworks.     

Exploring the Binding Proteins of Glycolipids with Bifunctional Chemical Probes

Glycolipids are important structural components of biological membranes and perform crucial functions in living systems, including signaling transduction and interaction with extracellular environment. However, the mechanistic exploration of glycolipids in vivo is challenging because they are not genetically encoded. Herein, we designed and synthesized a series of bifunctional monogalactosyldiacylglycerol (MGDG) probes as a model by introducing diazirine and terminal alkyne moieties on an aliphatic chain. In combination with proteome profiling and molecular modeling, we have demonstrated that MGDG alleviates inflammation by antagonizing TLR4.     

基于加权改进的AR模型的负载预测研究

负载预测在故障管理中有着十分重要的作用,通过对CPU负载以及内存使用率的预测可以对系统进行实时监控,预知未来时间段资源的可用性,发出异常告警;文中提出一种加权改进的自回归模型,通过对最小二乘法求出的参数进行加权处理,结合时间序列分析理论,建立一个负载预测模型,用于CPU负载和内存使用率的预测;实验证明,对AR模型的参数进行加权的方法优化了参数估计,预测误差减小了60%~80%。     

Enhanced surface free energy of polyimide fibers by alkali treatment and its interfacial adhesion behavior to epoxy resins

In this article, polyimide (PI) fibers were modified by alkali treatment, and PI fiber-reinforced epoxy composites were fabricated. The effects of different alkali treatment times on the surface properties of the PI fibers and the adhesion behaviors of PI fiber/epoxy composites were studied. The surface morphologies, chemical compositions, mechanical properties, and surface free energy of the PI fibers were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, single-fiber tensile strength analysis, and dynamic contact angle analysis, respectively. The results show that alkali treatment plays an important role in the improvement of the surface free energy and the wettability of PI fibers. We also found that, after the 3 min, 30 °C, 20 wt% NaOH solution treatment, the fibers possessed good mechanical properties and surface activities, and the interlaminar shear strength of the composites increased to 64.52 MPa, indicating good interfacial adhesion properties.     

Dye-sensitized solar cells with 3D flower-like α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-decorated reduced graphenes oxide as photoanodes

For the first time, we report a one-step fabrication of an environment-friendly approach to synthesize flower-like α-Fe₂O₃ hierarchical nanoparticles (NPs)/reduced graphene oxide (RGO) hybrids by combining the graphene oxide (GO) with the growth of α-Fe₂O₃ NPs. The GO sheet which possesses the functional group, such as hydroxyl (–OH) and carbonyl groups (–OOH), can be easily incorporated with the petal of the flower-like α-Fe₂O₃ in ethanol and water solution through a solvothermal process, during which GO is reduced to RGO without the addition of any strong reducing agent or requiring any post-high-temperature annealing process. The as-prepared samples are loose and porous with flower-like structure, and the RGO hybrids were wrapped up uniformly on the sheet of α-Fe₂O₃ NPs. To demonstrate the potential applications, we have fabricated dye-sensitized solar cells (DSSCs) from the as-synthesized hierarchical flower-like α-Fe₂O₃/RGO and investigated it for the photoanode of DSSCs. Results show that the hierarchical α-Fe₂O₃/RGO solar cell exhibits improved performances in comparison with the free α-Fe₂O₃ NPs. The enhancement of photovoltaic properties is attributed to the unique porous nature and good conductivity which allow more efficient diffusion of I^? ions and facilitate the transfer of electron in the network.     

Cavitation dose in an ultrasonic cleaner and its dependence on experimental parameters

The aluminum foil erosion method is widely used in cavitation activity studies of ultrasonic cleaners. However, owing to its limited sensitivity, it is difficult to observe the effects of various experimental parameters on the cavitation activity using this method. In the present work, a higher-sensitivity method for quantifying cavitation activity as a cavitation dose based on passive cavitation detection was presented. The influences of various factors (e.g., insonation duration, driving power, gas content, temperature and cleaning agents) were studied for this system. The results showed that the cavitation dose became unstable over long insonation times, and that the instability was more significant at high power. Generally, the cavitation activity could be enhanced by increasing the power, gas content, and the concentration of a cleaning agent. However, due to the exhaustion of the cavitation gas nuclei, the cavitation activity might tune to saturate of even decrease slightly when some impact parameters (e.g., acoustic driving power, gas content and the concentration of the cleaning agent) are above a certain level of each of these parameters.     

A highly selective and synthetically facile aqueous-phase cyanide probe

Disperse Orange 3 (4-(4-nitrophenylazo)aniline)-based chemosensor 1 has been prepared. This structurally simple receptor displays great selectivity for the cyanide anion over other common inorganic anions in aqueous environment and can detect cyanide in water sample at micromolar concentrations.     

Structural determination of two new sesquiterpenes biotransformed from germacrone by Mucor alternata

Eight transformed sesquiterpenes of germacrone by Mucor alternata were obtained. Their structures were characterized on the basis of spectral methods including 2D NMR. Among them, (1S, 4S, 5S, 10R)-isozedoarondiol (2) and (1R, 4S, 5S, 10R)-diepoxy-12-hydroxygermacrone (3) are new compounds.     

Promoting-mode free formalism for excited state radiationless decay process with Duschinsky rotation effect

In the present work, through the path integral of Gaussian type correlation function, a new formalism based on Fermi-Golden Rule for calculating the rate constant of nonradiative decay process with Duschinsky rotation effect in polyatomic molecules is developed. The advantage of the present path-integral formalism is promoting-mode free. In order to get the rate constant, a "transition rate matrix" needs to be calculated. The rate constant calculated previously is only an approximation of diagonal elements of our "transition rate matrix " . The total rate should be the summation over all the matrix elements.