Abstract The development of new antibacterial agents that can efficiently eradicate biofilms is of crucial importance to combat persistent and chronic bacterial infections. Herein, the fabrication of photoresponsive vesicles capable of the sequential release of nitric oxide (NO) and gentamicin sulfate (GS) is reported, which can not only efficiently disperse Pseudomonas aeruginosa ( P. aeruginosa ) PAO1 biofilm but also kill the planktonic bacteria. Well‐defined amphiphilic diblockcopolymers of poly(ethylene oxide)‐ b ‐poly(4‐((2‐nitrobenzyl)(nitroso)amino)benzyl methacrylate) (PNO) is first synthesized through atom transfer radical polymerization (ATRP). The PNO diblock copolymer self‐assembled into vesicles in aqueous solution, and a hydrophilic antibiotic of GS is subsequently encapsulated into the aqueous lumens of vesicles. The vesicles undergo visible light‐mediated N‐NO cleavage, releasing NO and disintegrating the vesicles with the release of the GS payload. The sequential release of NO and GS efficiently eradicate P. aeruginosa PAO1 biofilm and kill the liberated bacteria, showing a better antibiofilm effect than that of NO or GS alone.
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A palladium-catalyzed intramolecular hydroaminocarbonylation of 2-vinylbenzylamines in the absence of acidic or any other additives was realized via rational designing the catalytic system on the basis of mechanistic studies, which allows for the synthesis of a variety of six-membered lactams in good to excellent yields with high regioselectivity. The postulated palladium-hydride intermediate for initiating the hydroaminocarbonylation has been identified and directly used as a catalyst for the reaction. Further kinetic studies illustrated that the reaction rate is negative first-order-dependent on the substrate concentration with palladium hydride as a catalyst.
The detoxified beta1–epsilon (β1–ϵ) toxin protein of Clostridium perfringens type B provides protection from C. perfringens types B, C and D infections. Acetate is the primary by-product from the cell growth and expression of β1–ϵ protein. In the present study, the effects of pH and dissolved oxygen (DO) on the expression of β1--ϵ protein were investigated. Two-stage pH and DO control strategies were developed for the expression of β1–ϵ protein. The obtained results indicated that higher cell density and concentration of β1--ϵ protein, and lower accumulation of acetate were obtained when pH was maintained at a constant level of 6.5 (0–6 h) and 7.0 (6–16 h), and the DO level was maintained at 60% (0–6 h) and 30% (6–16 h). Furthermore, the impact of intermittent, DO feedback, pH feedback and glucose-stat feeding on the expression of β1–ϵ protein were studied. By using the DO feedback feeding, combined with the stage control of pH (6.5 for 0–6 h, 7.0 for 6–16 h) and DO (60% for 0–6 h, 30% for 6–16 h), the highest cell density of 2.045 (absorbance at 600 nm) and a β1–ϵ protein concentration of 63.24 mg/L were obtained, and the accumulation of acetate decreased to 0.872 g/L.
The study of liquid dynamics at mesoscopic scales is still strewn with difficulty due to limitations in theory and experiment. Historically, significant attention has been given to the analysis of space-time correlation functions and their frequency-Fourier transforms at a few discrete wave numbers. The massive computing power afforded by modern high performance computing clusters and the advent of a wide-angle neutron spin-echo spectrometer, however, have unlocked a more intuitive and fruitful approach to this problem. Using molecular dynamics simulations, here we demonstrate the benefits of spatiotemporally mapping intermediate scattering functions on a dense grid of correlation times and wave numbers. Four model systems are investigated: a Lennard-Jones liquid, a coarse-grained bead-spring polymer, a molten sodium chloride, and a poly(ethylene oxide) melt. We show that the spatiotemporal mapping approach is particularly useful for elucidating the mesoscopic dynamics in these liquids, where several underlying mechanisms, such as molecular relaxations, hydrodynamic modes, and nonhydrodynamic excitations, are potentially at play. Compared to the traditional method, direct visualization of density space-time correlation functions on two-dimensional color maps permits appraisals of complicated dynamical behavior at mesoscales in a global manner. For example, the scaling relations between space and time for different types of molecular motions can be straightforwardly identified on these plots, without any model-dependent analysis. Additionally, we show how theoretical ideas regarding collective mesoscopic dynamics, such as the classical hydrodynamic theory, the convolution approximation, and a recently proposed phenomenological model, can be discussed in terms of the global features of spatiotemporal maps of intermediate scattering functions. The new perspective offered by the spatiotemporal mapping method should prove useful for the study of liquid dynamics in general.
A novel kind of biodegradable polymer, cross-linked starch/polycaprolactone (PCL) blends was prepared, characterized and applied for biological denitrification. The results showed that the blends could be used as carbon source and biofilm carrier for denitrifying bacteria attachment. The temperature had a significant influence on denitrification rate, and the temperature constant was determined to be 0.0151 between 15 and 30°C in batch tests. The continuous fixed-bed experiments indicated that the average removal efficiency of NO3 was 92.51% at 25°C, while it was only 68.69% at 15°C. The formation of NH3-N was observed at both 15 and 25°C, but it kept below 1.0 mg/L. The excess release of dissolved organic compound was much lower at 15°C compared with that at 25°C. The scanning electron microscope results confirmed that both cross-linked starch and PCL could be utilized by denitrifying bacteria as carbon source for nitrate removal.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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