Cloning, expression, and purification of a Cu/Zn superoxide dismutase from Jatropha curcas.

We report cDNA cloning, expression, purification, and characterization of a novel Cu/ Zn superoxide dismutase (SOD) from Jatropha curcas leaves. The full-length cDNA of this SOD contained a 496-bp open-reading frame (ORF) encoding 162 amino acid residues. The recombinant plasmid containing the SOD coding sequence was introduced into Escherichia coli, and the SOD was expressed as a fusion protein. The recombinant SOD was purified from a high-density fed-batch culture using a combination of immobilized metal ion affinity chromatography (IMAC) and Sephadex G25 desalting chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis indicated that the recombinant SOD was a monomeric protein with a molecular mass of approximately 16.4 kDa. Isoelectric focusing showed that this SOD was a basic protein with pI values of 7.04, 7.33, 8.62, and 8.77. The activity of the SOD was stable at 70 degrees C for 10 min, and in a broad pH range from 4 to 9. The presence of urea (up to 8 M), guanidinium chloride (up to 6 M), and 2-mercaptoethanol (up to 8 mM) had little effect on the activity. The activity decreased gradually with increasing concentrations of imidazole, hydrogen peroxide, and ethylenediaminetetraacetic acid (EDTA). Atomic absorption spectrometry showed the presence of 0.239 copper and 0.258 zinc atoms, respectively, in the SOD polypeptide.

Design of Amine-Modified Zr-Mg Mixed Oxide Aerogel Nanoarchitectonics with Dual Lewis Acidic and Basic Sites for CO2/Propylene Oxide Cycloaddition Reactions.

The utilization of CO2 attracts much research attention because of global warming. The CO2/epoxide cycloaddition reaction is one technique of CO2 utilization. However, homogeneous catalysts with both Lewis acidic and basic and toxic solvents, such as DMF, are needed in the CO2/epoxide cycloaddition reaction. As a result, this study focuses on the development of heterogeneous catalysts with both Lewis acidic and basic sites for the CO2 utilization of the CO2/epoxide cycloaddition reactions without the addition of a DMF toxic solvent. For the first time, the Zr-Mg mixed oxide aerogels with Lewis acidic and basic sites are synthesized for the CO2/propylene oxide (PO) cycloaddition reactions. To further increase the basic sites, 3-Aminopropyl trimethoxysilane (APTMS) with -NH2 functional group is successfully grafted on the Zr-Mg mixed oxide aerogels. The results indicate that the highest yield of propylene carbonate (PC) is 93.1% using the as-developed APTMS-modified Zr-Mg mixed oxide aerogels. The as-prepared APTMS-modified Zr-Mg mixed oxide aerogels are great potential in industrial plants for CO2 reduction in the future.

Effects of Molecular Properties on Adsorption of Six-Carbon VOCs by Activated Carbon in a Fixed Adsorber.

Gravimetric adsorption equipment with a microbalance was used to measure the adsorption of volatile organic compounds (VOCs) by activated carbon from 288 to 313 K. VOCs [n-hexane, cyclohexane, 1-hexene, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, acetone, butanone, and 2-pentanone (Pentan-2-one)] were used as adsorbates in the adsorption system. Considering the geometric barrier, the critical diameter, and the boiling point, the adsorption capacities for six-carbon (C6) alkane isomers decrease in the order of n-hexane, 3-methylpentane, and 2-methylpentane. The adsorbates, including nonpolar or weakly polar substances, and substances with smaller geometric obstacles and smaller molecular weights, were more easily adsorbed by the activated carbon. However, the dipole-dipole interactive force at higher pressures resulted in a higher adsorption capacity for 1-hexene than for n-hexane. Both polarity and molecular size should be considered in the analysis of the adsorption of ketones by activated carbon. The adsorption equilibrium constants decreased with increases in temperature because a higher temperature was unfavorable for adsorption. The results for the Toth adsorption isotherm model fitted by the adsorption data showed that the experimental data and the Toth adsorption isotherm model were consistent with each other, as evidenced by the low deviation between the experimental data and those from the fitted model.

Dynamic determination of the concentration of volatile alcohols in a fixed bed of zeolite 13X by FT-IR.

A series of dynamic adsorptions of volatile methanol, ethanol, and iso-propanol (IPA) onto zeolite 13X were studied. Instead of traditional gas chromatography (GC), a gas-phase Fourier Transformation-IR (FT-IR) spectrometer was used to measure the evolution of concentrations of these volatile alcohols due to its quick response to the instantaneous changes of the gas concentration. Even though it has rarely been used in dynamic adsorption experiments in the literature, an FT-IR equipped with a constant-temperature gas cell was shown to be adequate to obtain breakthrough curves. In this study, the experiments were carried out at different gas flow rates and feed concentrations for each type of alcohol. Significant influences of the operating conditions on the breakthrough time, the shape of the breakthrough curve, and the uptake of each alcohol were found. A simple mathematical model proposed by Yoon and Nelson was applied to fit the experimental data. Good consistency between the experimental data and the regressed breakthrough curves was observed.

In situ DRIFT and kinetic studies of photocatalytic degradation on benzene vapor with visible-light-driven silver vanadates.

The visible-light active silver vanadates with different types of crystallines (Ag(4)V(2)O(7) and Ag(3)VO(4) phases) were synthesized by an environmentally friendly aqueous process. The parameters of hydrothermal temperature and hydrothermal time were tuned to maximize the photocatalytic efficiency for the decomposition of benzene vapor under visible-light irradiation. The quantum efficiencies of the photocatalysts are compared on the basis of the crystalline phases, surface area, intensity of surface hydroxyl groups, and Brönsted acid sites. From the results of DRIFTS studies, the photocatalytic activities strongly depend on the intensities of the Brönsted acidity and hydroxyl groups presented on the silver vanadates. The sample synthesized at 140 degrees C and 4h (HM140) exhibits the best photocatalytic activity; it has a reaction rate constant (k(app)) of 1.42 min(-1), much higher than that of P25 (k(app)=0.13 min(-1)). For an irradiation time of 720 min, the mineralization yields of benzene were 48% and 11% for HM140 and P25, respectively. Based on the short-term decrease of benzene concentration and the long-term increase of CO(2) concentration, the photocatalytic ability of the HM140 sample is significantly superior to that of P25. The highest activity can be attributed to the synergetic effects of the richest Brönsted acid sites, and a favorable crystalline phase combined with abundant surface hydroxyl groups.