Formation and tribological properties of two‐component ultrathin ionic liquid films on Si

Several single‐component and two‐component imidazolium ionic liquids (ILs) ultrathin films were formed on Si substrates by a dip‐coating and heat treatment process. The formation and surface properties of the films were analyzed by means of ellipsometric thickness measurement, X‐ray photoelectron spectra and atomic force microscope. The adhesive and nanotribological behaviors of the films were evaluated by a homemade colloidal probe. A ball‐on‐plate tribometer was used to test the microtribological performances of these films. As a result, the two‐component ILs ultrathin film containing 80% solid‐like ILs phase shows more homogenous surface morphologies and optimal micro/nano‐tribological properties as compared to single‐component ILs films, which is ascribed to a synergic effect between the steady solid‐like ILs phase as the backbone and the proper amount of flowable liquid‐like ILs phase. By studying the influence of various solid/liquid ILs ratios on tribological properties of the two‐component ILs films, we might find the way to design ILs films with excellent comprehensive tribological properties. Copyright © 2010 John Wiley & Sons, Ltd.     

Systematic screening and characterization of novel bufadienolides from toad skin using ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight mass spectrometry

During the discovery process of novel compounds, it is of significant importance to differentiate novel from known compounds in crude extracts before starting the time‐consuming process of purification. Bufadienolides are the main active components of the skin of the toad Bufo bufo gargarizans Cantor (toad skin), an important traditional Chinese medicine. The fragmentation behavior and mass spectra profiles of bufadienolides standards were investigated using ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight mass spectrometry (UPLC/ESI‐Q‐TOFMS). Several fragmentation rules were summarized and applied to characterize novel and known bufadienolides in toad skin. Characteristic substituent groups could be identified by both diagnostic ions and their relative abundance. Bufadienolide stereoisomers could be differentiated from positional isomers by comparing fragment abundance profiles. This was used to characterize new stereoisomers for known bufadienolides. A total of 39 bufadienolides were screened out using a systematic method developed in our laboratory. In addition to 19 known bufadienolides, 20 putative novel compounds, including 8 stereoisomers, were characterized. UPLC/Q‐TOFMS was demonstrated to be a powerful tool for the characterization of low‐abundance bufadienolides in complex samples. This study provides guidelines for the targeted isolation of novel bufadienolides from natural products. Copyright © 2010 John Wiley & Sons, Ltd.     

基于配体结构的Grb2-SH2抑制剂的结构优化:更高的活性、更少的电荷、更低的肽性

生长因子受体结合蛋白2(Grb2)在致癌基因Ras活化的信号传导通路中起着关键作用,目前被广泛认为是抗肿瘤药物设计的优秀靶标.对Grb2-SH2抑制剂的研究进展进行了综述,主要针对关键残基磷酸酪氨酸的高电荷性和多肽结构的低生物相容性两个缺陷,基于天然配体与Grb2-SH2相互作用的结构特征,围绕提高活性和简化结构开展的系统构效关系和合理结构优化研究,为进一步开发磷酸酪氨酸介导的Grb2-SH2抑制剂成为新型抗肿瘤药物提供结构和理论基础.     

Blind separation of fluorescence spectra using sparse non‐negative matrix factorization on right hand factor

Sparse non‐negative matrix factorization on right side factor (SNMF/R) has better performance in feature extraction than non‐negative matrix factorization. In this work, SNMF/R was first used to separate the overlapped three‐dimensional fluorescence spectra of polycyclic aromatic hydrocarbons mixtures in pure water, lake water, and river water, respectively. It is found that the similarity coefficients between the acquired three‐dimensional spectra and the corresponding reference spectra with random initials are all above 0.80; the recognition rate of SNMF/R is higher than that of PARAFAC and non‐negative matrix factorization algorithms, especially in the case of lake water and river water samples. In addition, SNMF/R does not need any initialization scheme designing during spectra separation. These results demonstrate that SNMF/R is an appropriate algorithm to separate the overlapped fluorescence spectra of polycyclic aromatic hydrocarbons in aquatic environment accurately and effectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Novel Copolymers of Styrene and Some Ring‐Substituted 2‐Cyano‐N,N‐Dimethyl‐3‐Phenyl‐2‐Propenamides

Electrophilic trisubstituted ethylene monomers, ring‐substituted 2‐cyano‐N,N‐dimethyl‐3‐phenyl‐2‐propenamides, RC₆H₄CH?C(CN)CON(CH₃)₂ (where R is 4‐(CH₃)₂N, 4‐CH₃CO₂, 4‐CH₃CONH, 2‐CN, 3‐CN, 4‐CN, 4‐(C₂H₅)₂N) were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and N,N‐dimethyl cyanoacetamide, and characterized by CHN elemental analysis, IR, ¹H‐ and ¹³C‐NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, ABCN at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C NMR, GPC, DSC, and TGA. High T_g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 300–450°C range.     

Novel Copolymers of Styrene and Alkoxy Ring‐Substituted 2‐Cyano‐N,N‐Dimethyl‐3‐Phenyl‐2‐Propenamides

Electrophilic trisubstituted ethylene monomers, alkoxy ring‐substituted 2‐cyano‐N,N‐dimethyl‐3‐phenyl‐2‐propenamides, RC₆H₄CH?C(CN)CON(CH₃)₂ (where R is 2‐OCH₃, 3‐OCH₃, 4‐OCH₃, 2‐OCH₂CH₃, 3‐OCH₂CH₃, 4‐OCH₂CH₂CH₃, 4‐OCH₂CH₂CH₂CH₃), were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and N,N‐dimethyl cyanoacetamide, and characterized by CHN elemental analysis, IR, ¹H‐ and ¹³C‐NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, ACBN at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C NMR, GPC, DSC, and TGA. High T_g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 300–450°C range.     

Novel Copolymers of Styrene and Halogen Ring‐Disubstituted 2‐Cyano‐N,N‐Dimethyl‐3‐Phenyl‐2‐Propenamides

Electrophilic trisubstituted ethylene monomers, halogen ring‐disubstituted 2‐cyano‐N,N‐dimethyl‐3‐phenyl‐2‐propenamides, RC₆H₃CH?C(CN)CON(CH₃)₂ (where R is 2,3‐dichloro, 2,4‐dichloro, 2,6‐dichloro, 3,4‐dichloro, 3,5‐dichloro, 2,3‐difluoro, 2,4‐difluoro, 2,6‐difluoro, 3,4‐difluoro, 3,5‐difluoro), were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and N,N‐dimethyl cyanoacetamide, and characterized by CHN elemental analysis, IR, ¹H‐ and ¹³C‐NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, ABCN at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C NMR, GPC, DSC, and TGA. High T_g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 300–450°C range.     

Synthesis and Characterization of Silicone Modified Polyurethane Surfactant Useable at High Temperature

A series of novel silicone modified polyurethane (Si-PU) surfactants were successfully synthesized by using hydroxypropyl-terminated polydimethylsiloxane (HPMS), polyethylene glycol (PEG), dimethylolpropionic acid (DMPA) and isophoronediisocyanate (IPDI). The chemical structure of the surfactant was confirmed by FTIR and ¹H-NMR. TEM photographs showed that the micelles of the Si-PU surfactants dispersed in aqueous solution were spherical with the particle size in the range of 100–400 nm. Surface tension measurements indicated that these surfactants had low surface tension to 29.9 mN·m^?1and a definite critical micelle concentration to, approximately 5.0×10^?4–7.5×10^?4mol·L^?1. When the content of HPMS was 20 wt%, the surfactant's, emulsifying performance was superior to the traditionally available Span80/Tween80 mixed emulsifiers. In addition to that, no phase transition temperature was detected from 20°C to 90°C by fluorescence probe and DSC measurements, confirming the high thermal stability of the micelles.     

Inclusion Interactions of Cucurbit[7]uril with Adenine and its Derivatives

Interactions of cucurbit[7]uril (Q[7] host) with guest adenine (g1), adenosine (g2) and 2′,3′-o-isopropylideneadenosine (g3) were studied in details by ¹H NMR, UV absorption spectroscopy, fluorescence spectroscopy and high performance liquid chromatography (HPLC) methods. We found that the suitable pH range for interaction was between 1 and 7, and the optimal pH range was between 2 and 4. The ¹H NMR analysis indicated that Q[7] selectively interacted with the adenine moiety of the guests g1 and g2, while Q[7] selectively interacted with the D-ribose sugar ring moiety of the guest g3. Moreover, ¹H NMR spectra showed that the exchange between the bound guest and the free guest was fast on the NMR time scale for the Q[7]-g1 and Q[7]-g2 systems. However, an obvious equilibrium between the bound host/guest and the unbound host/guest were observed in the Q[7]-g3 complex. Several methods were used to determine quantitatively the stability of the three host–guest inclusion complexes formed between Q[7] and the guests. The formation constants by UV and fluorescence were 1.90 × 10⁵ L mol^? 1 and 1.34 × 10⁵ L mol^? 1 for Q[7]-g1, 9.41 × 10⁴ L mol^? 1 and 4.24 × 10⁴ L mol^? 1 for Q[7]-g2, 4.50 × 10⁴ L mol^? 1 and 3.62 × 10⁴ L mol^? 1 for Q[7]-g3, respectively. HPLC method was also introduced to explore the interactions between Q[7] and the adenine and its derivatives. The formation constants of the host–guest inclusion complexes, as determined by HPLC, were 6.76 × 10⁴ L mol^? 1 for Q[7]-g1, 1.80 × 10⁴ L mol^? 1 for Q[7]-g2, 3.01 × 10⁴ L mol^? 1 for Q[7]-g3 respectively. Our study suggested that Q[7] could be a suitable host for the delivery of bioactive molecules, such as the adenine and its derivatives.