A comparative study of the collision induced dissociation and the electron capture dissociation of model peptides using ESI-FTMS

Tandem mass spectra of several model peptides, including KG3WG3K, NG3WG3N, RG7R, RG3WG3R, RG3DG3R, RG3EG3R, RG3FG3R and RG5WG5R were studied using both SORI-CID and ECD methods. By cross comparing the fragmentation pattern of these peptides using the same dissociation method and the same peptide using different dissociation methods, interesting spectral features that are related to the mechanisms of dissociation under SORI-CID and ECD conditions were extracted. Both dissociation methods were believed to be charge-directed. Due presumably to the stepwise ion activation, peptide ion dissociation under SORI-CID conditions was influenced mainly by "localized" hydrogen bonds. Consistent with previous literature findings, mobility proton model could be used to account for the spectral features observed. Substantial changes in the fragmentation patterns of these peptides were observed by using ECD methods. By postulating that the initial tertiary structures of the peptide ions were retained prior to electron capture process, the changes in fragmentation pattern could be attributed to the directing effect of the "global" hydrogen-bonding network. From the present results, no special preference was observed for cleavage at the backbone linkages adjacent to tryptophan residue over other inter-residual linkages. The previous reported nine-times cleavage preference at the C-terminal side of the tryptophan residue should therefore be attributed to some sequence specific phenomena.     

功能化多壁碳纳米管填充的凝胶电解质在染料敏化太阳能电池的应用

纯聚偏氟乙烯-六氟丙烯共聚物(PVDF-HFP)基凝胶电解质常常受制于低离子电导率,阻碍了其在染料敏化太阳电池(dye-sensitized solar cells,DSSCs)中的应用。 而利用纳米填充可提高凝胶电解质离子电导率及凝胶电解质DSSCs的性能。 本文使用功能化的多壁碳纳米管(f-MWCNT)作为PVDF-HFP凝胶电解质的纳米填充物,通过改变f-MWCNT的质量分数来研究其对电解质的离子电导率和离子扩散的影响,进而研究其对DSSCs的转化效率和长期稳定性的增强作用。 研究发现:质量分数0.5%的f-MWCNT明显提高了PVDF-HFP凝胶电解质的离子电导率和离子扩散系数。 并且,该凝胶电解质基DSSCs的光转换效率可达5.28%,相比于未填充的PVDF-HFP凝胶电解质基DSSCs(4.01%),其效率提高了31.7%。 42 d后,该电池依然可以保持最初转化效率的86.5%。 实验结果证实了f-MWCNT在纳米填充方面的巨大潜能,为采用纳米填充物提高凝胶电解质DSSCs的性能提供参考。     

A side-chain engineering strategy for constructing fluorescent dyes with direct and ultrafast self-delivery to living cells

Organic fluorescent dyes with excellent self-delivery to living cells are always difficult to find due to the limitation of the plasma membrane having rigorous selectivity. Herein, in order to improve the permeability of dyes, we utilize a side-chain engineering strategy (SCES): adjusting the side-chain length of dyes to fine-tune the adsorption and desorption processes on the membrane–aqueous phase interfaces of the outer and inner leaflets of the plasma membrane. For this, a family of fluorescent derivatives (SPs) was prepared by functionalizing a styryl-pyridinium fluorophore with alkyl side-chains containing a different carbon number from 1 to 22. Systematic experimental investigations and simulated calculations demonstrate that the self-delivery rate of SPs with a suitable length side-chain is about 22-fold higher in SiHa cells and 76-fold higher in mesenchymal stem cells than that of unmodified SP-1, enabling cell-imaging at an ultralow loading concentration of 1 nM and deep penetration in turbid tissue and in vivo. Moreover, the SCES can even endow a membrane-impermeable fluorescent scaffold with good permeability. Further, quantitative research on the relationship between Clog P and cell permeability shows that when Clog P is in the range of 1.3–2.5, dyes possess optimal permeability. Therefore, this work not only systematically reports the effect of side-chain length on dye delivery for the first time, but also provides some ideal fluorescent probes. At the same time, it gives a suitable Clog P range for efficient cellular delivery, which can serve as a guide for designing cell-permeant dyes. In a word, all the results reveal that the SCES is an effective strategy to dramatically improve dye permeability.

A side-chain engineering strategy can dramatically improve dye delivery by fine-tuning the adsorption and desorption abilities of the transmembrane process, enabling ultralow loading bioimaging and deep tissue penetration.     

Point-of-care detection of Microcystin-LR with a personal glucose meter in drinking water source

In this study, we described a point-of-care sensing protocol for rapid and sensitive detection of Microcystin-LR (MC-LR) in water by personal glucose meter. The POCT method possessed good reproducibility, selectivity, and stability, which may have potential for many other on-site detection applications.     

Highly Catalytic Enantioselective Addition of Diethyl Zinc to Aldehydes and Chalcone in the Presence of Chiral Ligands

Catalytic asymmetric carbon-carbon bond formation is one of the most important reactions and have attracted much attention to develop more efficient enantioselective C-C formation methods in organic synthesis. In this field, asymmetric addition of diethylzinc to aldehydes[1] and conjugate addition to enones[2] have drawn special interests and have been greatly developed. Regardless of it, much spaces in these areas still exist, so it needs more extensive and intensive researches for the purpose of as follows: (1) attaching ligands to a polymer for the easy separation of the catalysts so as to be able to allow very efficient recovery and reuse of the catalysts, and the possibility of carrying out the desired transfomation in continuous mode in a flow reactor, etc., (2) searching for novel chiral catalysts with such features as more suitable for more extensive substrates varieties, and more convenient and economical as well as possessing applicable prospect, and so on. Here we report some works in these areas done in our laboratory.     

Polymorphism of nylon‐6 in multiwalled carbon nanotubes/nylon‐6 composites

The effects of pristine and amino‐functionalized multiwalled carbon nanotubes (MWNTs) on the crystallization behaviors of nylon‐6 were investigated by differential scanning calorimetry and X‐ray diffraction. The results indicate the presence of polymorphism in nylon‐6 and its composites, which is dependent on the MWNTs concentration and the cooling rate. More MWNTs and slow cooling from the melt favors the formation of α crystalline form. With the increase in cooling rates, the crystallinity of neat nylon‐6 decreases, and that of the composites decreases initially but increases afterward. Moreover, the degree of crystallinity of the composites is higher than neat nylon‐6 under high cooling rates, counter to what is observed under low cooling rates. The heterogeneous nucleation induced by MWNTs and the restricted mobility of polymer chains are considered as the main factors. Furthermore, addition of MWNTs increases the crystallization rate of α crystalline form but amino‐functionalization of MWNTs weakens this effect. The influence of thermal treatment on the crystalline structure of MWNTs/nylon‐6 composites is also discussed. A γ–α phase transition takes place at lower temperature for MWNTs/nylon‐6 composites than for nylon‐6. The annealing peaks of the composites annealed at 160 °C are higher than that of neat nylon‐6, and the highest annealing peak is obtained for amino‐functionalized MWNTs/nylon‐6 composites. This phenomenon is closely related to the different nucleation and recrystallization behaviors produced by various MWNTs in confined space. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1499–1512, 2006     

The investigation of carbon nitride films annealed at different temperatures

The effects of thermal annealing on the component and microstructure of carbon nitride films deposited by vacuum cathodic arc method are reported. The bonding structure of the films is investigated by Raman spectroscopy, FTIR, XPS and valence band XPS. Upon annealing, the N content of the film drops gradually from original 31.0 to 17.0 at.% at 600 °C. The results of Raman spectroscopy, FTIR and valence XPS demonstrate that the films below 500 °C mainly consist of aromatic cluster component and polymeric component, which is rather stable upon the increasing of anealing temperatures. With the further increasing of the annealing temperatures from 400 to 600 °C, the fraction of polymeric component decreases and the aromatic component develops greatly. Meanwhile the films tend to transform towards the fullerene-like microstructure, which can be seen from the large separation of the N 1s peaks (>2.0 eV). As a result the N sp³ C bonds increase due to the rising of cross-linking between the graphite plane.     

掺杂和未掺杂氧化锌薄膜的拉曼光谱

利用拉曼光谱分别对不同衬底上,未掺杂和掺杂以及掺杂浓度不同的ZnO薄膜进行了系统的分析研究。其中ZnO薄膜均由溶胶-凝胶法制得,掺杂源为LiCl。测得的拉曼光谱显示,Pt/Ti/SiO2/Si衬底上生长的ZnO薄膜的拉曼特征峰(437cm-1)的强度明显高于SiO2/Si衬底上ZnO薄膜的拉曼特征峰的强度,说明Pt/Ti/SiO2/Si衬底上ZnO的晶化程度比SiO2/Si上ZnO的晶化程度高;但ZnO拉曼特征峰的位置和半高宽并没有发生变化,说明两种衬底上ZnO薄膜中应力大小没有发生变化。掺Li+后,580cm-1处的峰位向高频方向移动,且掺杂浓度越大频移量越大,说明掺杂已经在不同程度上引起了ZnO晶体中自由载流子浓度的变化。此外,还分析了掺Li+未在很大程度上引起ZnO晶格畸变的原因。     

Low order Crouzeix-Raviart type nonconforming finite element methods for the 3D time-dependent Maxwell’s equations

Two Crouzeix-Raviart type nonconforming elements are used in a finite element scheme as well in a mixed finite element scheme for time-dependent Maxwell’s equations in three dimensions. The error estimates are obtained under anisotropic meshes, which are the same as those for conforming elements under regular meshes.     

Finite groups with transitive semipermutability

A group G is said to be a T-group (resp. PT-group, PST-group), if normality (resp. permutability, S-permutability) is a transitive relation. In this paper, we get the characterization of finite solvable PST-groups. We also give a new characterization of finite solvable PT-groups.