The synthesis of L-ascorbyl flurbiprofenate was achieved by esterification and transesterification in nonaqueous organic medium with Novozym 435 lipase as biocatalyst. The conversion was greatly ...influenced by the kinds of organic solvents, speed of agitation, catalyst loading amount, reaction time, and molar ratio of acyl donor to L-ascorbic acid. A series of solvents were investigated, and tert-butanol was found to be the most suitable from the standpoint of the substrate solubility and the conversion for both the esterification and transesterification. When flurbiprofen was used as acyl donor, 61.0% of L-ascorbic acid was converted against 46.4% in the presence of flurbiprofen methyl ester. The optimal conversion of L-ascorbic acid was obtained when the initial molar ratio of acyl donor to ascorbic acid was 5 : 1. kinetics parameters were solved by Lineweaver-Burk equation under nonsubstrate inhibition condition. Since transesterification has lower conversion, from the standpoint of productivity and the amount of steps required, esterification is a better method compared to transesterification.
Chemical fixation of carbon dioxide with epoxides to form cyclic carbonates proceeds very effectively under mild conditions by using a chitosan-supported zinc chloride catalyst in conjunction with ...1-butyl-3-methylimidazole halides (BMImX) without any organic solvents. Reaction temperature, carbon dioxide pressure, effects of co-catalysts and the molar ratio of catalyst to co-catalyst were investigated. The optimum reaction conditions were 110
°C and 1.5
MPa, and BMImBr was the best co-catalyst. The catalyst system was recycled and reused.
A task-specific basic ionic liquid, BmimOH, has been introduced as a catalyst for the aza-Michael addition of aromatic amines and
N-heterocycles to cyclic or acyclic ketones under neat conditions. ...The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency.
Esterification of starch was carried out to expand the usefulness of starch for a myriad of industrial applications. Lipase B from Candida antarctica, immobilized on macroporous acrylic resin ...(Novozym 435), was used for starch esterification in two reaction systems: micro-solvent system and solvent-free system. The esterification of corn starch with palmitic acid in the solvent-free system and micro-solvent system gave a degree of substitution (DS) of 1.04 and 0.0072 respectively. Esterification of corn starch with palmitic acid was confirmed by UV spectroscopy and IR spectroscopy. The results of emulsifying property analysis showed that the starch palmitate with higher DS contributes to the higher emulsifying property (67.6%) and emulsion stability (79.6%) than the native starch (5.3% and 3.9%). Modified starch obtained by esterification that possesses emulsifying properties and has long chain fatty acids, like palmitic acid, has been widely used in the food, pharmaceutical and biomedical applications industries.
Preparation of gold nanoparticles with a narrow size distribution has enormous importance in nanotechnology. Methanobactin (Mb) is a copper-binding small peptide that appears to function as an agent ...for copper sequestration and uptake in methanotrophs. Mb can also bind and catalytically reduce Au (III) to Au (0). In this study, we demonstrate a facile Mb-mediated one-step synthetic route to prepare monodispersed gold nanoparticles. Continuous reduction of Au (III) by Mb can be achieved by using hydroquinone as the reducing agent. The gold nanoparticles have been characterized by UV-visible spectroscopy. The formation and the surface plasmon resonance properties of the gold nanoparticles are highly dependent on the ratio of Au (III) to Mb in solution. X-ray photoelectron spectroscopy (XPS), fluorescence spectra and Fourier transform-infrared spectroscopy (FT-IR) spectra suggest that Mb molecules catalytically reduce Au (III) to Au (0) with the concomitant production of gold nanoparticles, and then, Mb statically adsorbed onto the surface of gold nanoparticles to form an Mb-gold nanoparticles assembly. This avoids secondary nucleation. The formed gold nanoparticles have been demonstrated to be monodispersed and uniform by transmission electron microscopy (TEM) images. Analysis of these particles shows an average size of 14.9 nm with a standard deviation of 1.1 nm. The gold nanoparticles are extremely stable and can resist aggregation, even after several months.
Iris lactea var. chinensis (I. lactea var. chinensis) is tolerant to accumulations of cadmium (Cd) and lead (Pb). In this study, the transcriptome of I. lactea var. chinensis was investigated under ...Cd or Pb stresses. Using the gene ontology database, 31,974 unigenes were classified into biological process, cellular component and molecular function. In total, 13,132 unigenes were involved in enriched Encyclopedia of Genes and Genomes (KEGG) metabolic pathways, and the expression levels of 5904 unigenes were significantly changed after exposure to Cd or Pb stresses. Of these, 974 were co-up-regulated and 1281 were co-down-regulated under the two stresses. The transcriptome expression profiles of I. lactea var. chinensis under Cd or Pb stresses obtained in this study provided a resource for identifying common mechanisms in the detoxification of different heavy metals. Furthermore, the identified unigenes may be used for the genetic breeding of heavy-metal tolerant plants.
Differential gene expression analyses of the I. lactea var. chinensis transcriptome after exposure to Pb and Cd are shown in Venn diagrams. (A) Up-regulated unigenes; (B) Down-regulated unigenes. Display omitted
•Iris lactea var. chinensis is tolerant to accumulations of cadmium and lead.•The transcriptome of Iris lactea var. chinensis was investigated under cadmium or lead stress.•Provide a resource for identifying common mechanisms in the detoxification of different heavy metals.
Activation and reconstruction of the spinal cord circuitry is important for improving motor function following spinal cord injury. We conducted a case series study to investigate motor function ...improvement in 14 patients with chronic spinal cord injury treated with 4 weeks of unilateral (right only) cortical intermittent theta burst stimulation combined with bilateral magnetic stimulation of L3-L4 nerve roots, five times a week. Bilateral resting motor evoked potential amplitude was increased, central motor conduction time on the side receiving cortical stimulation was significantly decreased, and lower extremity motor score, Berg balance score, spinal cord independence measure-III score, and 10 m-walking speed were all increased after treatment. Right resting motor evoked potential amplitude was positively correlated with lower extremity motor score after 4 weeks of treatment. These findings suggest that cortical intermittent theta burst stimulation combined with precise root stimulation can improve nerve conduction of the corticospinal tract and lower limb motor function recovery in patients with chronic spinal cord injury.
Hydrolysis of propylene carbonate to 1,2-propylene glycol was performed by using a SBIL catalyst. It was found that more than 99% yield and selectivity were obtained in the presence of SBIL at the ...optimum conditions. Additionally, the catalyst could be reused at least up five times with slight loss of catalytic activity.
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Hydrolysis of propylene carbonate to 1,2-propylene glycol was performed by using a SBIL catalyst. The effects of temperature, reaction time, the molar ratio of water to propylene carbonate, choice of catalyst, and the amount of catalyst were investigated. It was found that more than 99% yield and selectivity were obtained in the presence of SBIL under the optimum conditions. Additionally, the catalyst could be reused at least up to five times with slight loss of catalytic activity.
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