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At least 19 recordsLinked to original sources
PubMed2006

Facile "green" synthesis, characterization, and catalytic function of beta-D-glucose-stabilized Au nanocrystals.

We present a straightforward, economically viable, and "green" approach for the synthesis and stabilization of relatively monodisperse Au nanocrystals with an average diameter of 8.2 nm (standard deviation, SD=2.3 nm) by using nontoxic and renewable biochemical of beta-D-glucose and by simply adjusting the pH environment in aqueous medium. The beta-D-glucose acts both as reducing agent and capping agent for the synthesis and stabilization of Au nanocrystals in the system. The UV/Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), electron diffraction (ED), and X-ray diffraction (XRD) techniques were employed to systematically characterize Au nanocrystals synthesized. Additionally, it is shown that these beta-D-glucose-stabilized Au nanocrystals function as effective catalyst for the reduction of 4-nitrophenol in the presence of NaBH4 (otherwise unfeasible if only the strong reducing agent NaBH4 is employed), which was reflected by the UV/Vis spectra of the catalytic reaction kinetics.

Glucose↗
PubMed2003

Completely "green" synthesis and stabilization of metal nanoparticles.

In the present Communication, a completely "green" synthetic method for producing silver nanoparticles is introduced. The process is simple, environmentally benign, and quite efficient. By gentle heating of an aqueous starch solution containing silver nitrate and glucose, we produce relatively monodisperse, starched silver nanoparticles. beta-d-Glucose serves as the green reducing agent, while starch serves as the stabilization agent.

Journal Article↗
PubMed2005

'Green' synthesis of nitro alcohols catalyzed by solid-supported tributylammonium chloride in aqueous medium.

A series of 1-aryl-2-nitroalkan-1-ols (5a-m; Table 2) was prepared in yields of 64-94% by Henry reaction between aromatic aldehydes and nitroalkanes in the presence of a dual catalytic system of KOH and polystyrene-supported tributylammonium chloride (PsTBAC; 2). The reactions were performed either in H2O containing 10% of THF or, in the case of liquid reagents (aldehydes and nitroalkanes), in neat H2O at room temperature. The immobilized phase-transfer catalyst, designed to be used for large-scale industrial processes, could be easily separated from the products, and effectively re-used several times, basically without loss in activity.

Catalysis↗
PubMed2006

A novel one-pot 'green' synthesis of stable silver nanoparticles using soluble starch.

Stable silver nanoparticles have been synthesized by using soluble starch as both the reducing and stabilizing agents; this reaction was carried out in an autoclave at 15 psi, 121 degrees C for 5 min. Nanoparticles thus prepared are found to be stable in aqueous solution over a period of three months at room temperature (approximately 25 degrees C). The size of these nanoparticles was found to be in the range of 10-34 nm as analyzed using transmission electron micrographs. The X-ray diffraction analysis revealed the face-centred cubic (fcc) geometry of silver nanoparticles. Iodometric titration confirmed the entrapment of silver nanoparticles inside the helical amylose chain. These silver nanoparticles embedded in soluble starch produced a typical emission peak at 553 nm when excited at 380 nm. The use of environmentally benign and renewable materials like soluble starch offers numerous benefits of eco-friendliness and compatibility for pharmaceutical and biomedical applications.

Amylose↗
PubMed2006

At point of use sono-electrochemical generation of hydrogen peroxide for chemical synthesis: the green oxidation of benzonitrile to benzamide.

At point of use generation of synthetically useful quantities of hydrogen peroxide in a non-optimized sono-electrochemical cell is reported. Proof-of-concept of the use of this procedure for green synthesis is given through the oxidation of benzonitrile to benzamide with yields similar to those obtained via bulk chemical synthesis.

Journal Article↗
PubMed1976

Relation between Paramylum Content and the Length of the Lag Period of Chlorophyll Synthesis during Greening of Dark-grown Euglena gracilis.

Euglena cells, strains Z and bacillaris, were grown in the dark under various nutritional deficiencies. After 3 days of nondivision, cells were transferred to the light, and the following parameters were measured: the paramylum content at the time of illumination (zero time), the rate of paramylum consumption during the first 10 hours of greening, and the length of the lag phase of chlorophyll synthesis. Similar results were obtained with both strains and can be summarized as follows. (a) The use of various nutritional deficiencies allows the control, to a certain extent, of the amount of paramylum present at zero time. (b) The rate of paramylum consumption is proportional to the cellular paramylum content for values in excess of 50 picograms/cell. (c) The length of the lag phase increases rapidly when the cellular content of paramylum decreases below 50 picograms. This period can be greatly diminished by the addition of an exogenous organíc carbon source. (d) The amount of paramylum (rate of paramylum consumption x length of lag phase) consumed during the lag phase is around 5 to 10 picograms/cell for cells which contain less than 50 picograms of paramylum/cell. It increases when the cellular paramylum content increases, this increment being more rapid for bacillaris than for Z cells.

Journal Article↗
PubMed1966

Effects of Light Intensity on Photosynthetic Carboxylative Phase Enzymes and Chlorophyll Synthesis in Greening Leaves of Hordeum vulgare L.

The effects of various light intensities on in vivo increases in activities of phosphoriboisomerase, phosphoribulokinase and ribulose-1, 5-diP carboxylase and on synthesis of chlorophyll were studied in greening leaves of Hordeum vulgare L.Each enzyme was already present in dark-grown plants, but further increases in activities required both a light treatment of the intact plant and a favorable temperature. The amount of enzymatic activity and chlorophyll developed was governed by light intensity.Measured activities of phosphoriboisomerase and ribulose 1,5-diP carboxylase were highly correlated with synthesis of chlorophyll at all intensities studied. Measured activity of phosphoribulokinase was correlated with synthesis of chlorophyll only at saturating or near saturating light intensities. At decreasing light intensities the response curves of this enzyme differed from those of chlorophyll and of phosphoriboisomerase and ribulose-1, 5-diP carboxylase. A lag period of phosphoribulokinase increased with decreasing light intensity. After the lag period a rapid rate of increase occurred which did not level off during 48 hours of illumination. Thus, a different control mechanism may be operative in inducing increased activity of this enzyme.

Journal Article↗
PubMed2005

Multiple losses of neutral C14H14 in the tandem mass spectrometry of several perbenzyl ether intermediates in the synthesis of green tea constituents.

Electrospray and matrix-assisted laser desorption/ionization (MALDI) tandem mass spectrometry (MS/MS) experiments were used to investigate an unusual fragmentation in collision-induced dissociation (CID) of sodiated and potassiated perbenzyl ether intermediates obtained in the total synthesis of gallate ester constituents of green tea. Prominent fragments correspond to multiple sequential losses of neutral C14H14 that were not observed in the protonated and ammoniated species, that instead present fragment ion series in which members are separated by C7H6. High-resolution MALDI quadrupole time-of-flight (Q-TOF) and electrospray-Fourier transform mass spectrometry (FTMS) were used to confirm elemental compositions of these and related ions.

Esters↗
PubMed1975

Protoheme turnover and chlorophyll synthesis in greening barley tissue.

Studies in which (14)C-labeled precursors were fed to etiolated barley leaves (Hordeum vulgare L. var. Proctor) yielded chlorophyll and protoheme having similar specific radioactivities. These findings indicate: (a) there appears to be a rapid turnover of protoheme in the absence of net synthesis; (b) both pigments probably originate from a single 5-aminolevulinic acid pool; (c) the efficient utilization of glutamate-1-(14)C and the relatively poor utilization of glycine-2-(14)C suggest that 5-aminolevulinic acid is probably synthesized by a pathway other than 5-aminolevulinic acid synthetase (succinyl CoA-glycine succinyltransferase) in agreement with previously published work; (d) protoheme turnover appears to be faster under conditions which allow for rapid chlorophyll accumulation; (e) difference spectra indicate that mitochondrial cytochromes make a relatively minor contribution to the total heme in barley leaves. These findings are discussed in the light of current knowledge about tetrapyrrole regulation in photosynthetic organisms.

Journal Article↗
PubMedDate not supplied

Synthesis of green fluorescent protein-ricin and monitoring of its intracellular trafficking.

We performed genetic engineering to fuse enhanced green fluorescent protein (EGFP) to the N terminus of RTA, expressed the fusion protein in Escherichia coli, purified and reassociated EGFP-RTA with plant RTB, and purified EGFP-ricin by size exclusion HPLC. The fusion heterodimer was able to bind galactosides, intoxicate cells, and show strong fluorescence. Mammalian cells incubated with EGFP-ricin showed strong cell surface fluorescence at 4 degrees C and, on incubation at 37 degrees C, distributed initially to endosomes and then to Golgi vesicles. Variable sensitivity of mammalian cells to ricin and ricin fusion proteins may be due in part to different patterns of intracellular routing. Cells were incubated with ricin or EGFP-ricin, and inhibition of protein synthesis was measured. Human hepatocellular carcinoma Hep3B cells were 10-fold more sensitive to ricin and 85-fold more sensitive to EGFP-ricin than human epidermoid carcinoma KB cells. Epifluorescence microscopy of cells incubated with EGFP-ricin showed greater localization of the fluorescence signal in the Golgi compartments in Hep3B cells than in KB cells. These data support a model requiring a Golgi-dependent step in cell intoxication by ricin. The work further identifies the usefulness of green fluorescent protein fusions in the study of retrograde transport of internalized peptides.

Cell Survival↗
PubMed2003

Light and cytokinin play a co-operative role in MGDG synthesis in greening cucumber cotyledons.

The current research investigated the regulation of monogalactosyldiacylglycerol (MGDG) biosynthesis, catalyzed by MGDG synthase (MGD) (UDP-galactose:1,2-diacylglycerol 3-beta-D-galactosyltransferase; EC 2.4.1.46), during chloroplast development in cucumbers (Cucumis sativus L. cv. Aonagajibai). In etiolated seedlings, white light induced a transient increase in MGD mRNA, followed by a subsequent increase in enzyme activity. MGDG, digalactosyldiacylglycerol (DGDG), and linolenic acid (18 : 3) of both MGDG and DGDG accumulated in a light-dependent manner. Early light-dependent induction of MGD protein was also identified in isolated chloroplasts. When cotyledons were detached from seedlings, these light-induced changes diminished. However, when a synthetic cytokinin, benzyladenine, was added to the detached cotyledons, a transient increase in MGD mRNA and a linear increase in the enzyme activity were induced even in the dark. Galactolipids subsequently accumulated to some extent and 18 : 3 content also increased. MGDG fully accumulated in detached cotyledons with co-treatment of light and a cytokinin. Red light (>600 nm) and far-red light (>700 nm) both induced an increase in MGD mRNA and enzyme activity but far-red light did not induce an accumulation of MGDG. These results suggest that (1). galactolipid biosynthesis is regulated by the cooperation of light and a cytokinin; (2). the accumulation of MGDG requires cytokinin in addition to light; (3). a red light (600-700 nm) dependent factor is necessary for the maximal galactolipid accumulation in addition to increase in MGD transcript and activity.

Adenine↗
PubMed1975

Regulation of chlorophyll synthesis in the green alga golenkinia.

Chlorophyll synthesis in Golenkinia is inhibited 10-fold by growth in darkness on acetate or by growth on elevated concentrations of acetate in the light, particularly if the growth medium contains low levels of nitrogen. Glucose has no such inhibitory effect. delta-Aminolevulinic acid, with a maximal effect at 0.01 m, but not its precursors, overrides the inhibitory effect of acetate and darkness, restoring chlorophyll synthesis. Glycine, succinate, and alpha-ketoglutarate, the precursors tested, all enter the cell. Cells forming chlorophyll produce significantly more aminolevulinic acid than do cells becoming bleached, further indicating the important regulatory role of this compound. Cyclic AMP has no effect on chlorophyll synthesis. These results are compared with those obtained studying other algae, and a mechanism relating light and acetate to chlorophyll formation is proposed.

Journal Article↗
PubMed2006

Synthesis of MCM-41 from coal fly ash by a green approach: influence of synthesis pH.

The present study reports a green synthesis method for preparing pure (free of fly ash) and ordered MCM-41 materials from coal fly ash at room temperature (25 degrees C) during 24 h of reaction. It was shown that the impurities in the coal fly ash were not detrimental to the formation of MCM-41 at the tested conditions. The influence of initial synthesis pH on material properties of calcined MCM-41 samples was investigated by various techniques such as XRF, XPS, XRD, FTIR, DR-UV-vis, solid state NMR, N2 physisorption, TG-DTA, SEM and TEM. The experimental results showed that the amount of trace elements such as Al, Na, Ti and Fe incorporated into the sample increased with synthesis pH value. More aluminum species were incorporated with tetrahedral coordination in the framework under a high pH value. The particle size of the sample decreased with the synthesis pH value. Samples synthesized at high pH values had a larger pore size and were more hydrothermally stable than those at low pH values. From thermal analysis, it was observed that the synthesized MCM-41 samples showed a high thermal stability. These properties made the synthesized MCM-41 suitable for further processing into more useful materials in a wide range of applications.

Carbon↗