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In this work, we investigated the functions of structural modules within alginate lyase by truncating an endo-type alginate lyase into two successive catalytic modules. The effects of module deletion on biochemical characteristics and product distributions were further investigated. The N-terminal module (Aly7B-CDI) exhibited no activity toward alginate, polyM or polyG, but the C-terminal module (Aly7B-CDII) retained its activity. The full-length enzyme (Aly7B) and its truncated counterpart (Aly7B-CDII) had similar substrate specificities, but Aly7B-CDII had lower activity. Moreover, the activity of Aly7B was much higher than Aly7B-CDII at 30°C. Aly7B-CDII, however, possessed higher optimal pH and better pH stability than the full-length enzyme. The final degradation products for Aly7B were unsaturated di-, tri- and tetra-oligosaccharides, and those for Aly7B-CDII were unsaturated mono-, di-, tri-, tetra- and penta-oligosaccharides. Therefore, the potential impact of the noncatalytic module Aly7B-CDI on the catalytic module Aly7B-CDII was further elucidated by characterizing Aly7B and its truncations. These data contribute to the functional understanding of these differing modules.

The exploitation of a high-activity and low-cost bifunctional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) as the cathode catalyst is a research priority in metal–air batteries. Herein, a novel bifunctional hybrid catalyst of hortensia-like MnO2 synergized with carbon nanotubes (CNTs) (MnO2/CNTs) is controllably synthesized by reasonably designing the crystal structure and morphology as well as electronic arrangement. On the basis of these strategies, the hybrid accelerates the reaction kinetics and avoids the change of structures. As expected, MnO2/CNTs exhibit a remarkable ORR and OER activity [low ORR Tafel slope: 71 mV dec–1, low OER Tafel slope: 67 mV dec–1, and small potential difference (ΔE): 0.85 V] and a long-term stability, which should be attributed to its unique morphology, K+ ions in the 2 × 2 tunnels, and synergistic effect between MnO2 and CNTs. Notably, in zinc–air batteries (ZABs), aluminum–air batteries (AABs), and magnesium–air batteries (MABs), the c...

In this study, a series of acidic or alkaline polypeptide chains were designed and grafted onto DEG-AM resin using Fmoc solid-phase synthesis to study the relationship between enzyme conformation and carrier surface charge. β-d-glucosidase (βGase) was then immobilized onto these modified carriers by adsorption. Each form of immobilized βGase showed decreasing specific activity compared to that of the free. It could be attributed to both the changes in the enzyme conformation and the decrease in mass transfer efficiency. The optimum temperature of free βGase, DEG@B3-βGase is 55 °C, which of DEG@A3-βGase is 65 °C and they all have the highest activity at pH 5. The Ea values ​​of free βGase, DEG@A3-βGase, and DEG@B3-βGase are 0.546 kJ/mol, 0.224 kJ/mol, and 0.446 kJ/mol, and the Km values were 1.30 mmol/L, 1.44 mmol/L and 2.63 mmol/L, respectively. It shows that free βGase and DEG@A3-βGase are more similar. Meanwhile, the free βGase (1.0 g/L, pH 5.0) stored at 4 °C has a shorter half-life (t1/2), which is only 9 days. However, the half-life of DEG@B3-βGase and DEG@A3-βGase is 20 days and over 60 days, indicating that the negative charged surface was conducive to maintenance of the structure and catalytic property of βGase.

Ulvan, a kind of polyanionic heteropolysaccharide consisting of 3-sulfated rhamnose, uronic acids (iduronic acid and glucuronic acid) and xylose, has been widely applied in food and cosmetic industries. In addition, ulvan can be converted into fermentable monosaccharides through the cascade system of carbohydrate-active enzymes. Ulvan lyases can degrade ulvan into ulvan oligosaccharides, which is the first step in the fully degradation of ulvan. Various ulvan lyases have been cloned and characterized from marine bacteria and grouped into five polysaccharide lyase (PL) families, namely: PL24, PL25, PL28, PL37 and PL40 families. The elucidation of the biochemical characterization, action pattern and catalytic mechanism of ulvan lyase would definitely enhance our understanding of the deep utilization of marine bioresource and marine carbon cycling. In this review, we summarized the recent progresses about the source and biochemical characteristics of ulvan lyase. Additionally, the structural characteristics and catalytic mechanisms have been introduced in detail. This comprehensive information should be helpful regarding the application of ulvan lyases.

Copper oxides (CuO x ) nanoparticles dispersed on activated carbon (AC) were prepared by using vapor-phase methanol as the reducing agent. The CuO x /AC as prepared exhibited an enhanced catalytic activity in oxidative carbonylation of methanol to dimethyl carbonate (DMC). The catalytic performance was significantly influenced by reduction conditions including temperature and time. With the similar selectivity of DMC, the space time yield (STY) under optimal reduction conditions reached up to 408 mg g −1 h −1 , which is superior to conventional methods such as thermolysis and solvothermal reduction. Based on the characterization results of XRD, TEM and XPS, the good copper dispersion and high Cu + content obtained by vapor-phase methanol reduction were mainly responsible for the high catalytic activity.

Macroporous n -type silicon photocathodes were successfully prepared using an electrochemical etching method under constant current electrolysis at 40 mA cm −2 . We found that comparing with planar n -type and etching p -type silicon photocathodes, the macroporous n -type silicon photocathodes exhibited considerably higher photocurrent response and photoelectrochemical(PEC) performance in terms of H 2 generation under visible light irradiation without requiring a catalyst or a sacrificial agent. This study provides an alternative method of preparing porous silicon and introduces a new photocatalyst or support for noble-metal nanophotocatalysts for PEC water splitting.

Multi-wall carbon nanotubes (MWCNTs) were synthesized on carbon fiber cloth by chemical vapor deposition using natural gas as the carbon source and FeSO4 · 7H2O powder as the catalyst precursor. Scanning and transmission electron microscopy and Raman spectroscopy were used to characterize the product. Small catalyst particles were observed on the top of the tubes. The MWCNTs were dispersed uniformly and aligned perpendicular to the cloth. They had a high crystallinity, and few impurities and defects. The density and structure of the MWCNTs on the cloth can be controlled by deposition temperature and time. [New Carbon Materials 2013, 28(6): 421–427]

The SN2 reaction of enantiomerically pure sulfonates with the tunable complex of R3N–R′COOH in toluene has been extensively studied. It was revealed that the molar ratio of the tertiary amines and carboxylic acids in the complex of R3NR′COOH is crucial for the SN2 reaction, and should be tuned for each sulfonate to give the best yield. Fifteen sulfonates 1 and 3–13 (Scheme 2) were prepared and transformed into 22 corresponding inverted esters 2 and 14–24 (Scheme 2) in good to high yields.

The pyrolysis of biomass is a promising way for production of bio-gasoline if the stability and quality problems of the bio-crudeoil can be solved by catalytic cracking and reforming. In this paper, an on-line infrared spectrum was used to study the characteristics of catalytic pyrolysis with the following preliminary results. The removal of C=O of organic acid is more difficult than that of aldehydes and ketones. HUSY/gamma-Al2O3 and REY/gamma-Al2O3 catalysts exhibited better deoxygenating activities while HZSM-5/gamma-Al2O3 catalyst exhibited preferred selectivities for production of iso-alkanes and aromatics. Finally, possible mechanisms of biomass catalytic pyrolysis are discussed as well. (c) 2007 Ran Zhong Yao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

The reactions of cyclomaltoheptaose (β-cyclodextrin) and maleic anhydride were investigated, and the resulting products characterized by i.r., proton, and carbon-13 n.m.r. spectroscopy. The 13 C-n.m.r. spectra show preferential esterification at HO-6 under various conditions of temperature and concentration of reactants and of catalyst. An increase of temperature, catalyst concentration, or initial molar ratio of maleic anhydride to cyclodextrin increases the rate of esterification.

The hydration reaction by microbial method is the crisis of the procedure of acrylamide production from acrylonitrile. This research studied the enzyme catalytic kinetics and de-active kinetics of nitrile hydratase in the type of free cell. Firstly, the effects of the concentration of cells, the temperature, pH value, the concentration of acrylonitrile and the concentration of acrylamide on the activity of nitrile hydratase was investigated. The result is that the temperature and the concentration of acrylamide are the most important among these factors. The activity of the nitrile hydratase was 5659 u/mL (broth) at 28 degrees C; the counterpart was only 663 u/mL (broth) at 5 degrees C. And the activity of NHase in solution of 45% acrylamide was just about half of that in solution of 5% acrylamide. After study on the relation of temperature and the reaction speed, It was found that the activation energy of the hydration of NHase was 65.57 kJ.mol-1. This paper studied the effects of concentration of cells, temperature, pH value, concentrations of acrylonitrile and acrylamide on the deactivation of Nhase, as well as the related enzyme de-active kinetics. The result also showed that the temperature and the concentration of acrylamide are the most important among these factors. In solution of 35% acrylamide, the residual activity was about 0% of the original value after 55 h; but in solution of 10% acrylamide, after the same period of time, the residual activity was 50% of the original one. It was also found that the concentration of acrylonitrile had little effect on the stability of NHase. The coefficient of deactivation at 28 degrees C was 21.77 times of the one at 5 degrees C. Correlating the temperature and the coefficient of deactivation, the activation energy of the de-active reaction was found to be 92.28 kJ.mol-1.