Antibacterial Constituents from Isodon Excisoides

Two new ent‐kaurane diterpenoids, taihangexcisoidesin C (1) and its acetonide, taihangexcisoidesin D (2), along with 9 known compounds were isolated from the leaves of Isodon excisoides. The structures of the new compounds were elucidated using 1D and 2D NMR spectroscopy analysis. Compounds 3‐6 and 8‐9 were tested for their antibacterial activity against Escherichia coli, Staphylococcus aureus, S. epidermidis and S. saprophyticus. Compound 6 showed inhibitory effects on Staphylococcus aureus, S. epidermidis and S. saprophyticus MIC values 32, 16 and 16 μg/mL, respectively. All of the compounds didn't show effects on Escherichia coli (MIC > 10 mg/mL).     

Immobilization of Modified Papain with Anhydride Groups on Activated Cotton Fabric

Papain (EC 3.4.22.2) has been chemically modified using two novel reagents including different anhydrides of 1,2,4-benzenetricarboxylic and pyromellitic acids. Then, the modified papain was immobilized on the activated cotton fabric by a two-step method. The number of free amino groups in the modified protein was investigated through the 2,4,6-trinitrobenzenesulfonic acid method. Energy dispersive spectrometer was used to characterize papain immobilization. Some parameters of both modified and native papain immobilized on cotton fabric, such as optimum temperature, optimum pH, and the stabilities for reservation in various detergents were studied and compared. The resultant papain had its optimum pH shifted from 6.0 to 9.0. Compared with immobilized native papain, the thermal stability and the resistance to alkali and washing detergent of immobilized modified enzyme were improved considerably. When the concentration of detergent was 20 mg/ml, the activity of the immobilized pyromellitic papain retained about 40% of its original activity, whereas the native papain was almost inhibited. This work demonstrated that the cotton fabric immobilized modified papain has potential applications in the functional textiles field.     

Layer-by-layer assembly of porphyrin/layered double hydroxide ultrathin film and its electrocatalytic behavior for H2O2

The ordered ultrathin film based on iron(III) porphyrin and Co–Al layered double hydroxide (Co–Al LDH) nanosheets has been fabricated via the layer-by-layer (LBL) method. The film modified electrode demonstrates a couple of well-defined reversible redox peaks attributed to Co(III)/Co(II), with iron(III) porphyrin serving as an efficient mediator for facilitating the electron transfer. Furthermore, it exhibits excellent electrocatalytic behavior for H₂O₂ with a wide linear range of response, high sensitivity and low detection limit.     

Current Rectification in Temperature‐Responsive Single Nanopores

Herein we demonstrate a fully abiotic smart single‐nanopore device that rectifies ionic current in response to the temperature. The temperature‐responsive nanopore ionic rectifier can be switched between a rectifying state below 34 °C and a non‐rectifying state above 38 °C actuated by the phase transition of the poly(N‐isopropylacrylamide) [PNIPAM] brushes. On the rectifying state, the rectifying efficiency can be enhanced by the dehydration of the attached PNIPAM brushes below the LCST. When the PNIPAM brushes have sufficiently collapsed, the nanopore switches to the non‐rectifying state. The concept of the temperature‐responsive current rectification in chemically‐modified nanopores paves a new way for controlling the preferential direction of the ion transport in nanofluidics by modulating the temperature, which has the potential to build novel nanomachines with smart fluidic communication functions for future lab‐on‐chip devices.     

Preparation and characterization of molecularly imprinted microspheres for dibutyl phthalate recognition in aqueous environment

Molecularly imprinted microspheres (MIMs) were prepared by suspension polymerization for the binding and recognition of dibutyl phthalate (DBP). DBP was used as the template molecule, methacrylic acid as the functional monomer, ethylene dimethacrylate (EDMA) as the linking agent, PVA as the dispersing agent, and Span 60 as the surfactant. The MIMs were characterized with electron microscope scanning and rebinding experiments. The Scatchard plot revealed that the template‐polymer system has a two‐site binding behavior with dissociation constants of 4.05 and 0.515 mmol/L. The MIMs exhibited the highest selective rebinding to DBP at 736.85 μg/g. The recoveries of the MIM‐SPE column for DBP extraction was 94.75–101.9% with the RSD of 1.5–7.3%, indicating the feasibility of the prepared MIMs for DBP extraction. Finally, the method developed was used to analyze the trace levels of phthalate in aqueous environment samples.     

Improving Gene Delivery Efficiency of Bioreducible Poly(amidoamine)s via Grafting with Dendritic Poly(amidoamine)s

Dendritic poly(amidoamine)s (PAMAM)s were introduced into the side chains of disulfide‐containing poly(amidoamine)s via repetitive Michael addition and amidation. The bioreducible poly(amidoamine)s grafted with dendritic polyamidoamines showed high buffer capacity, low cytotoxicity and strong DNA binding ability at low N/P ratio. They were able to condense DNA into small sized polycation/DNA complexes, which degraded and released the incorporated DNA under reductive conditions. In comparison to the original disulfide‐containing poly(amidoamine) with aminoethyl side chain, the grafting of the bioreducible poly(amidoamine) with dendrimer greatly improved the transfection efficiencies of 293T and HeLa cells with foreign DNA at various N/P ratios. The structure–gene delivery property relations of dendrimer‐grafted polycations will provide valuable insight into the design of highly efficient and less toxic polycationic gene carriers.

     

Simultaneous determination of NOGE-related and BADGE-related compounds in canned food by ultra-performance liquid chromatography–tandem mass spectrometry

An improved analytical method enabling rapid and accurate determination and identification of bisphenol F diglycidyl ether (novolac glycidyl ether 2-ring), novolac glycidyl ether 3-ring, novolac glycidyl ether 4-ring, novolac glycidyl ether 5-ring, novolac glycidyl ether 6-ring, bisphenol A diglycidyl ether, bisphenol A (2,3-dihydroxypropyl) glycidyl ether, bisphenol A (3-chloro-2-hydroxypropyl) glycidyl ether, bisphenol A bis(3-chloro-2-hydroxypropyl) ether, and bisphenol A (3-chloro-2-hydroxypropyl) (2,3-dihydroxypropyl) ether in canned food and their contact packaging materials has been developed by using, for the first time, ultra-performance liquid chromatography coupled with tandem mass spectrometry. After comparison of electrospray ionization and atmospheric pressure chemical ionization in positive and negative-ion modes, tandem mass spectrometry with positive electrospray ionization was chosen to carry out selective multiple reaction monitoring analysis of novolac glycidyl ethers, bisphenol A diglycidyl ether, and its derivatives. The analysis time is only 5.5 min per run. Limits of detection varied from 0.01 to 0.20 ng g(-1) for the different target compounds on the basis of a signal-to-noise ratio (S/N) = 3; limits of quantitation were from 0.03 to 0.66 ng g(-1). The relative standard deviation for repeatability was <8.01%. Analytical recovery ranged from 87.60 to 108.93%. This method was successfully applied to twenty samples of canned food and their contact packaging materials for determination of migration of NOGE, BADGE, and their derivatives from can coatings into food.     

Probing polymer surfaces and interfaces using sum frequency generation vibrational spectroscopy - a powerful nonlinear optical technique

Sum frequency generation (SFG) vibrational spectroscopy has been proved to be a powerful technique which substantially impacts on many research areas in surface and interfacial sciences. This paper reviews the recent progress of applying this nonlinear optical technique in the studies of polymer surfaces and interfaces. The theoretical background of SFG is introduced first. Current applications of SFG in polymer science are then described in more detail to demonstrate the significance of this technique. Finally, a short summary is presented on this relatively new but widely applicable spectroscopic technique.     

Direct analysis in real time (DART) mass spectrometry of nucleotides and nucleosides: elucidation of a novel fragment [C<Subscript>5</Subscript>H<Subscript>5</Subscript>O]<Superscript>+</Superscript> and its in-source adducts

Direct analysis in real time (DART) mass spectrometry is a recently developed innovative technology, which has shown broad applications for fast and convenient analysis of complex samples. Due to the ease of sample preparation, we have recently initiated an investigation of the feasibility of detecting nucleotides and nucleosides using the DART-AccuTOF instrument, which we will refer to as the DART mass spectrometer. Our experimental results reveal that the ions representing the intact molecules of nucleotides are not detectable in either positive-ion or negative-ion mode. Instead, all four natural nucleotides fragment in the DART ion source, and a common fragment ion, [C₅H₅O]⁺ (1), is observed, which is probably formed via multiple-elimination reactions. Interestingly, 1 can form adducts with nucleobases in different molar ratios in the DART ion source. In contrast to nucleotides, the ions representing the intact molecules of nucleosides are detected in both positive-ion and negative-ion mode using DART mass spectrometry. Surprisingly, the fragmentation pattern of nucleosides is different from that of nucleotides in the DART ion source. In the cases of nucleosides (under positive-ion conditions), the production of 1 is not observed, indicating that the phosphate group plays an important role for the multiple eliminations observed in the spectra of nucleotides. The in-source reactions described in the present work show the complexity of the conditions in the DART ion source, and we hope that our results illustrate a better understanding about DART mass spectrometry.