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51.
Cytochrome P450 enzymes generally functionalize inert C−H bonds, and thus, they are important biocatalysts for chemical synthesis. However, enzymes that catalyze both aliphatic and aromatic hydroxylation in the same biotransformation process have rarely been reported. A recent biochemical study demonstrated the P450 TxtC for the biosynthesis of herbicidal thaxtomins as the first example of this unique type of enzyme. Herein, the detailed characterization of substrate requirements and biocatalytic applications of TxtC are reported. The results reveal the importance of N-methylation of the thaxtomin diketopiperazine (DKP) core on enzyme reactions and demonstrate the tolerance of the enzyme to modifications on the indole and phenyl moieties of its substrates. Furthermore, hydroxylated, methylated, aromatic DKPs are synthesized through a biocatalytic route comprising TxtC and the promiscuous N-methyltransferase Amir_4628; thus providing a basis for the broad application of this unique P450.  相似文献   
52.
The adsorption capacity of polyaspartamide (PAA) and multi‐wall carbon nanotubes with polyaspartamide (MWNT‐PAA) was investigated through a packed bed column with the flowing of flue gas composed of 15 % CO2, 5 % O2 and the balance N2. The adsorption performed at 25 °C, 110 kPa and inlet gas flow rate of 60 mL/min resulted in high CO2 adsorption capacity of 5.70 and 10.20 mmol‐CO2/g for PAA and MWNT‐PAA, respectively. The adsorption kinetics was very high, so 7 min were enough for the effluent gas to reach the breakthrough after saturation. The consistency of adsorbents in recurring regeneration was successful through a continuous TSA system of 10 cycle adsorption‐desorption with temperatures of 25–100 °C. The evaluation of heat through differential scanning calorimetry (DSC) resulted in exothermic adsorption with heat release of 45.14 kJ/mol and 124.38 kJ/mol for PAA and MWNT‐PAA, respectively. The heat release was found favourable to promote the desorption as the temperature could rise after adsorption. This is an advantage for energy efficiency, as it depicts the potential of energy recovery. Thus, both adsorbent PAA and MWNT‐PAA were demonstrated to be promising for CO2 adsorption capture in post‐combustion.  相似文献   
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The morphology of porous silicon is studied by scanning electron microscopy (SEM) by making an oxide replica of the pore structure. Highly branched n-type porous silicon samples were prepared and a replica was formed by oxidation of the pores followed by selective removal of the silicon substrate to expose the oxide pores. Scanning and transmission electron microscopy images confirmed many previously held assumptions about porous silicon formation, including the fractal structure and crystallographic propagation; they also provided a clearer understanding of the details of pore formation. The replica procedure also provides a platform for a more facile and comprehensive analysis of the porous silicon morphology.  相似文献   
55.
The fabrication of carbon nanostructures by direct writing with a scanning force microscope is described. A conductive atomic force tip is used to collect carbon from a glassy carbon substrate and redeposit it onto a gold thin film under voltage control. The resulting patterns are examined with atomic force microscopy and Auger electron spectrometry. Writing of carbon lines with widths as small as 40 nm is demonstrated.  相似文献   
56.
Barley contains high levels of soluble dietary fibre, including mixed linked 1→3, 1→4β-D -glucans (β-glucan). An extract of β-glucan from waxy, hulless barley containing 56% total dietary fibre (TDF) was incorporated into flour tortillas, cornstarch pudding and apple granola bars to provide 2 g soluble fibre as β-glucan per serving. The foods were tested for objective functional properties. Flour tortillas with β-glucan were incorporated into rat diets and compared to diets containing an equivalent amount of cellulose, to test the fibre effect on growth and lipid metabolism parameters. Rats fed β-glucan tortillas had lower feed consumption and body weight (P<0·05) compared to those fed the cellulose tortillas, although feed/gain ratios were not different (P>0·05). Plasma LDL-cholesterol of rats fed β-glucan was lower (P<0·05) than cellulose-fed controls, although total cholesterol and triglycerides did not differ (P>0·05). Rats fed β-glucan tortillas had higher (P<0·05) faecal fat excretion, suggesting impairment of intestinal fat absorption. Liver composition data showed lower (P<0·05) levels of total lipid and cholesterol in β-glucan-fed rats. The results suggest that the barley β-glucan concentrate has potential as a food ingredient to provide supplemental soluble fibre which may be beneficial in reducing plasma LDL-cholesterol in humans. © 1998 SCI.  相似文献   
57.
Objective: Describe the development and preliminary evaluation of a safety awareness program for women with disabilities. Design: Baseline and postintervention questionnaires administered to a sample of women who completed a safety awareness program. Participants: Seven women with diverse disabilities. Intervention: Eight interactive sessions designed to increase protective factors. Setting: Community site for persons with disabilities. Main Outcomes: Safety self-efficacy, safety skills, social support/isolation, and safety promoting behaviors. Results: Significant increases from baseline to postintervention were found on measures of self-efficacy and safety skills. Although not statistically significant, improvements were also found in safety promoting behavior. Conclusion: Despite the small sample, findings suggest that participation in a safety awareness program may improve protective factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
58.
Fourier transform infrared (FT-IR) attenuated total reflection (ATR) imaging has been successfully used to identify individual mineral components of ancient Maya paint. The high spatial resolution of a micro FT-IR-ATR system in combination with a focal plane array detector has allowed individual particles in the paint to be resolved and identified from their spectra. This system has been used in combination with micro-Raman spectroscopy to characterize the paint, which was found to be a mixture of hematite and silicate particles with minor amounts of calcite, carbon, and magnetite particles in a sub-micrometer hematite and calcite matrix. The underlying stucco was also investigated and found to be a combination of calcite with fine carbon particles, making a dark sub-ground for the paint.  相似文献   
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The aim of this study was to produce a natural pigment powder with functional properties. To optimise the spray-drying process, a central composite design with 17 treatments was used, in which the independent variables were the inlet drying air temperature (138–202 °C), the feed flow rate (20–67 mL/min), and the concentration of the carrier (maltodextrin, 100–300 g/kg of extract). The dependent variables were the moisture content, hygroscopicity, and anthocyanin retention. The samples were analysed by: anthocyanin and phenolic content; antioxidant properties based on the ORAC and DPPH assays; antimicrobial activity against Staphylococcus aureus, Listeria monocytogenes, Salmonella enteritidis, and Escherichia coli; and inhibitory activity against arginase, an enzyme produced by Leishmania amazonensis. The experimental design was not significant or predictive in the ranges studied. The selected samples contained high concentrations of anthocyanins and phenolics, and high antioxidant capacities. In addition, they exhibited antimicrobial activity against three of the four microorganisms tested, and some of the samples also exhibited a bactericidal effect. Moreover, the powders exerted inhibitory activity (64–69%) against arginase. The results obtained in this study suggest that the jabuticaba depulping residue could be used to produce a natural pigment with functional properties.  相似文献   
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