Formation and Out-of-Equilibrium,High/Low State Switching of a Nitroaldol Dynamer in Neutral Aqueous Media

The nitroaldol reaction is demonstrated as an efficient dynamic covalent reaction in phosphate buffers at neutral pH. Rapid equilibration was recorded with pyridine-based aldehydes, and dynamic oligomerization could be achieved, leading to nitroaldol dynamers of up to 17 repeating units. The dynamers were applied in a coherent stimuli-responsive molecular system in which larger dynamers transiently existed out-of-equilibrium in a neutral aqueous system rich in formaldehyde, controlled by nitromethane.     

A novel particle sampling system for physico-chemical and toxicological characterization of emissions

Several studies have shown that combustion-derived fine particles cause adverse health effects. Previous toxicological studies on combustion-derived fine particles have rarely involved multiple endpoints and a detailed characterization of chemical composition. In this study, we developed a novel particle sampling system for toxicological and chemical characterization (PSTC), consisting of the Dekati Gravimetric Impactor (DGI) and a porous tube diluter. Physico-chemical and toxicological properties of the particles emitted from various combustion sources were evaluated in two measurement campaigns. First, the DGI was compared with the High-Volume Cascade Impactor (HVCI) and to the Dekati Low-Pressure Impactor (DLPI), using the same dilution system and the same sampling conditions. Only small differences were observed in the mass size distributions, total particulate matter (PM), and particulate matter with diameter smaller than 1 um (PM(1)) concentrations and geometric mass mean diameters (GMMD) between these three impactors. Second, the PSTC was compared with the HVCI sampling system, which has been optimal for collection of particulate samples for toxicological and chemical analyses. Differences were observed in the mass size distributions, total PM and PM(1) emissions, and GMMDs, probably due to the different sampling and dilution methods as well as different sampling substrates which affected the behavior of semi-volatile and volatile organic compounds. However, no significant differences were detected in the in vitro measurements of cytotoxicity between the samples collected with the PSTC and the HVCI systems. In measurements of genotoxicity, significant differences between the two sampling systems were seen only with the particles emitted from the sauna stove. In conclusion, due to compact size, PSTC is an applicable method for use in particle sampling as part of the toxicological and chemical characterization of particulate emissions from different combustion sources. It offers some advantages compared to the previously used high-volume sampling methods including compactness for field measurements, simple preparation of sample substrates and high extraction efficiency.     

Analysis of Toxaphene (PCC) and Chlordane in Biological Samples by NCI Mass Spectrometry

Abstract

Several recent reports indicate that both toxaphene (polychlorocamphene, PCC) and chlordane are widespread pollutants in our environment. These insecticides, both complex mixtures of chlorinated hydrocarbons, are difficult to separate from each other. Thus the analyses of them in environmental samples are difficult and furthermore complicated by interferences from other chlorinated hydrocarbons such as PCB and DDT compounds. Mass fragmentography using the negative ions formed by chemical ionization proved to be useful to selectively detect the toxaphenes and the chlordanes without interferences from DDT. High concentrations of PCB still influence on the results and have to be removed in the clean-up procedure.     

Cytochrome c/polyelectrolyte multilayers investigated by E-QCM-D: effect of temperature on the assembly structure

Protein multilayers, consisting of cytochrome c (cyt c) and poly(aniline sulfonic acid) (PASA), are investigated by electrochemical quartz crystal microbalance with dissipation monitoring (E-QCM-D). This technique reveals that a four-bilayer assembly has rather rigid properties. A thickness of 16.3 ± 0.8 nm is calculated with the Sauerbrey equation and is found to be in good agreement with a viscoelastic model. The electroactive amount of cyt c is estimated by the deposited mass under the assumption of 50% coupled water. Temperature-induced stabilization of the multilayer assembly has been investigated in the temperature range between 30 and 45 °C. The treatment results in a loss of material and a contraction of the film. The electroactive amount of cyt c also decreases during heating and remains constant after the cooling period. The contraction of the film is accompanied by the enhanced stability of the assembly. In addition, it is found that cyt c and PASA can be assembled at higher temperatures, resulting in the formation of multilayer systems with less dissipation.     

Surface functionalization of nanofibrillated cellulose using click-chemistry approach in aqueous media

In the present work, amino functionalized nanofibrillated cellulose (NFC) was prepared using click-chemistry in aqueous reaction conditions. First, reactive azide groups were introduced on the surface of NFC by the etherification of 1-azido-2,3-epoxypropane in alkaline water/isopropanol-mixture at ambient temperature. Then the azide groups were reacted with propargyl amine utilizing copper catalyzed azide-alkyne cycloaddition (CuAAC), leading to pH-responsive 1,2,3-triazole-4-methanamine decorated NFC. The reaction products were characterized using Fourier transform infrared spectroscopy, elemental analysis and X-ray photoelectron spectroscopy. The presence of the attached azide groups was also confirmed by reacting them with 5-(dimethylamino)-N-(2-propyl)-1-naphthalenesulfonamide by CuAAC, yielding highly fluorescent NFC. In addition, atom force microscopy and rheology studies confirmed that the original NFC nanostructure was maintained during the synthesis.     

Antibacterial and Oxidative Stress-Protective Effects of Five Monoterpenes from Softwood

Volatile organic compounds (VOC) affect the quality of indoor air. Terpenes and especially monoterpenes are the main molecules emitted from softwood material (coniferous species), which is widely used in construction. The corneal epithelium is one of the first human membranes to encounter VOCs in the air. Moreover, the industrial use of pleasant-scented monoterpenes in cosmetics, food, and detergents exposes people to monoterpenes in their daily lives. In the present study, the health effective properties of five monoterpenes from softwood were tested; cytotoxicity and oxidative stress-protective effects of α- and β-pinenes, R- and S-limonene, and 3-carene were tested in a human corneal epithelial (HCE) cell model system and with two additional in vitro antioxidant tests: oxygen radical absorbance capacity (ORAC) and hydrogen peroxide (H₂O₂) scavenging. Antibacterial efficacies were tested with two bioluminescent bacterial biosensor strains (Escherichia coli K12+pcGLS11 and Staphylococcus aureus RN4220+pAT19) and with minimum inhibitory concentration (MIC) test against Escherichia coli. Only very high concentrations of monoterpenes (0.3–0.5 mg/mL) demonstrated cytotoxicity against HCE cells. Contrary to the original hypothesis, monoterpenes did not exhibit strong antioxidant properties in tested concentrations. However, biosensors and MIC tests indicated clear antibacterial activities for all tested monoterpenes.     

Correlation of aluminum doping and lithiation temperature with electrochemical performance of LiNi1-xAlxO2 cathode material

Journal of Solid State Electrochemistry - This article presents a process for producing LiNi1-xAlxO2 (0 <  ×  < 0.05) cathode material with...