Ionic liquids as recycling solvents for the synthesis of magnetic nanoparticles

This work describes an easy synthesis (one pot) of MFe(2)O(4) (M = Co, Fe, Mn, and Ni) magnetic nanoparticles MNPs by the thermal decomposition of Fe(Acac)(3)/M(Acac)(2) by using BMI center dot NTf(2) (1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) or BMI center dot PF(6) (1-n-butyl-3-methylimidazolium hexafluorophosphate) ionic liquids (ILs) as recycling solvents and oleylamine as the reducing and surface modifier agent. The effects of reaction temperature and reaction time on the features of the magnetic nanomaterials (size and magnetic properties) were investigated. The growth of the MNPs is easily controlled in the IL by adjusting the reaction temperature and time, as inferred from Fe(3)O(4) MNPs obtained at 150 degrees C, 200 degrees C and 250 degrees C with mean diameters of 8, 10 and 15 nm, respectively. However, the thermal decomposition of Fe(Acac)(3) performed in a conventional high boiling point solvent (diphenyl ether, bp 259 degrees C), under a similar Fe to oleylamine molar ratio used in the IL synthesis, does not follow the same growth mechanism and rendered only smaller NPs of 5 nm mean diameter. All MNPs are covered by at least one monolayer of oleylamine making them readily dispersible in non-polar solvents. Besides the influence on the nanoparticles growth, which is important for the preparation of highly crystalline MNPs, the IL was easily recycled and has been used in at least 20 successive syntheses.

Spin-wave fluctuations in ferrimagnetic Mg(x)Fe(3-x)O(4) nanoparticles

We have performed a systematic study of the magnetic properties of a series of ferrimagnetic nanoparticles of Mg(x)Fe(3-x)O(4) (0.8 <= x <= 1.5) prepared by the combustion reaction method. The magnetization data can be well fitted by Bloch's law with T(3/2). Bloch's constant B determined from the fitting procedure was found to increase with Mg content x from similar to 3.09 X 10(-5) K(-3/2) for x = 0.8 to 6.27 X 10(-5) K(-3/2) for x=1.5. The exchange integral J(AB) and the spin-wave stiffness constant D of Mg(x)Fe(3-x)O(4) nanoparticles were also determined as similar to 0.842 and 0.574 meV and 296 and 202 meV angstrom(2) for specimens with x=0.8 and 1.5, respectively. These results are discussed in terms of cation redistribution among A and B sites on these nanostructured spinel ferrites. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3359709]

Possible hyperdeformed band in (36)Ar observed in (12)C+(24)Mg elastic scattering

Fifteen strongly oscillating angular distributions of the elastic scattering of (12)C + (24)Mg at energies around the Coulomb barrier (E(c.m). = 10.67-16.00 MeV) are reproduced by adding five Breit-Wigner resonance terms to the l = 2, 4, 6, 7, and 8 elastic S matrix. The nonresonant, background elastic scattering S matrix S(l)(0) is calculated using the Sao Paulo potential. The J = 2, 4, 6, 7, and 8 (h) over bar molecular resonances fit well into a rotational molecular band, together with other higher lying resonances observed in the (16)O + (20)Ne elastic scattering. We propose that the presently observed, largely deformed molecular band corresponds to the hyperdeformed band, which has been found previously in alpha-cluster calculations, as well as in a new Nilsson model calculation. Systematic study of its possible clusterizations predicts the preference of the (12)C + (24)Mg and (16)O + (20)Ne molecular structure, in accordance with our present results.

On the template synthesis of nanostructured inorganic/organic hybrid films

Prussian Blue has been introduced as a mediator to achieve stable, sensitive, reproducible, and interference-free biosensors. However, Na(+), Li(+), H(+), and all group II cations are capable to block the activity of Prussian Blue and, because Na(+) can be found in most human fluids, Prussian Blue analogs have already been developed to overcome this problem. These analogs, such as copper hexacyanoferrate, have also been introduced in a conducting polypyrrole matrix to create hybrid materials (copper hexacyanoferrate/polypyrrole, CuHCNFe/Ppy) with improved mechanical and electrochemical characteristics. Nowadays, the challenges in amperometric enzymatic biosensors consist of improving the enzyme immobilization and in making the chemical signal transduction more efficient. The incorporation of nanostructured materials in biosensors can optimize both steps and a nanostructured hybrid CuHCNFe/Ppy mediator has been developed using a template of colloidal polystyrene particles. The nanostructured material has achieved sensitivities 7.6 times higher than the bulk film during H(2)O(2) detection and it has also presented better results in other analytical parameters such as time response and detection limit. Besides, the nanostructured mediator was successfully applied at glucose biosensing in electrolytes containing Prussian Blue blocking cations. (C) 2008 The Electrochemical Society.

Role of beta-alanine supplementation on muscle carnosine and exercise performance

ARTIOLI, G. G., B. GUALANO, A. SMITH, J. STOUT, and A. H. LANCHA, JR. Role of beta-Alanine Supplementation on Muscle Carnosine and Exercise Performance. Med. Sci. Sports Exerc., Vol. 42, No. 6, pp. 1162-1173, 2010. In this narrative review, we present and discuss the current knowledge available on carnosine and beta-alanine metabolism as well as the effects of beta-alanine supplementation on exercise performance. Intramuscular acidosis has been attributed to be one of the main causes of fatigue during intense exercise. Carnosine has been shown to play a significant role in muscle pH regulation. Carnosine is synthesized in skeletal muscle from the amino acids L-histidine and beta-alanine. The rate-limiting factor of carnosine synthesis is beta-alanine availability. Supplementation with beta-alanine has been shown to increase muscle carnosine content and therefore total muscle buffer capacity, with the potential to elicit improvements in physical performance during high-intensity exercise. Studies on beta-alanine supplementation and exercise performance have demonstrated improvements in performance during multiple bouts of high-intensity exercise and in single bouts of exercise lasting more than 60 s. Similarly, beta-alanine supplementation has been shown to delay the onset of neuromuscular fatigue. Although beta-alanine does not improve maximal strength or (V) over dotO(2max), some aspects of endurance performance, such as anaerobic threshold and time to exhaustion, can be enhanced. Symptoms of paresthesia may be observed if a single dose higher than 800 mg is ingested. The symptoms, however, are transient and related to the increase in plasma concentration. They can be prevented by using controlled release capsules and smaller dosing strategies. No important side effect was related to the use of this amino acid so far. In conclusion, beta-alanine supplementation seems to be a safe nutritional strategy capable of improving high-intensity anaerobic performance.

Performance of different immobilized lipases in palm oil biodiesel synthesis

Performance of different immobilized lipases in palm oil biodiesel synthesis. Optimized conditions for palm oil and ethanol enzymatic biodiesel synthesis were determined with different immobilized lipases SiO(2)-PVA-immobilized lipase from Pseudomonas fluorescens and acrylic resin-immobilized lipase, Novozym (R) 435, from Candida antartica, in solvent-free medium. A full factorial design assessed the influence of temperature (42 - 58 degrees C) and ethanol: palm oil (6:1 - 18:1) molar ratio on the transesterification yield. Main effects were adjusted by multiple regression analysis to linear models and the maximum transesterification yield was obtained at 42 degrees C and 18:1 ethanol: palm oil molar ratio. Mathematical models featuring total yield for each immobilized lipase were suitable to describe the experimental results.

Multipoint covalent immobilization of lipase on chitosan hybrid hydrogels: influence of the polyelectrolyte complex type and chemical modification on the catalytic properties of the biocatalysts

This work aimed at the production of stabilized derivatives of Thermomyces lanuginosus lipase (TLL) by multipoint covalent immobilization of the enzyme on chitosan-based matrices. The resulting biocatalysts were tested for synthesis of biodiesel by ethanolysis of palm oil. Different hydrogels were prepared: chitosan alone and in polyelectrolyte complexes (PEC) with kappa-carrageenan, gelatin, alginate, and polyvinyl alcohol (PVA). The obtained supports were chemically modified with 2,4,6-trinitrobenzene sulfonic acid (TNBS) to increase support hydrophobicity, followed by activation with different agents such as glycidol (GLY), epichlorohydrin (EPI), and glutaraldehyde (GLU). The chitosan-alginate hydrogel, chemically modified with TNBS, provided derivatives with higher apparent hydrolytic activity (HA(app)) and thermal stability, being up to 45-fold more stable than soluble lipase. The maximum load of immobilized enzyme was 17.5 mg g(-1) of gel for GLU, 7.76 mg g(-1) of gel for GLY, and 7.65 mg g(-1) of gel for EPI derivatives, the latter presenting the maximum apparent hydrolytic activity (364.8 IU g(-1) of gel). The three derivatives catalyzed conversion of palm oil to biodiesel, but chitosan-alginate-TNBS activated via GLY and EPI led to higher recovered activities of the enzyme. Thus, this is a more attractive option for both hydrolysis and transesterification of vegetable oils using immobilized TLL, although industrial application of this biocatalyst still demands further improvements in its half-life to make the enzymatic process economically attractive.

Synthesis, characterization and evaluation of phosphorylated resins in the removal of Pb(2+) from aqueous solutions

Phosphinic-derivative poly(styrene-co-divinylbenzene)-based on PS-DVB copolymers with different porosity degrees have been prepared by aromatic electrophilic substitution reaction using PCl(3)/AlCl(3) followed by base-promoted hydrolysis. The phosphorylation reaction was analyzed by infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG/DTG). In addition, the phosphorous content of the phosphorylated copolymers was determined by spectrophotometry using the method based on sodium molybdate reactant so that the extension of that modification could be assessed. The performance of the phosphorylated resins in the extraction of Pb(2+) from aqueous solutions in a batch system was also evaluated. The Pb(2+) content was determined by atomic absorption spectrometry (AAS). These materials presented excellent extraction capacity under the contact time of 30 min and pH 6.

Improved Bioprocess with CHO-hTSH Cells on Higher Microcarrier Concentration Provides Higher Overall Biomass and Productivity for rhTSH

Since the recombinant thyroid-stimulating hormone (rhTSH) is secreted by stably transfected Chinese hamster ovary (CHO-hTSH) cells, a bioprocess consisting of immobilizing the cells on a substrate allowing their multiplication is very suitable for rhTSH recovering from supernatants at relative high degree of purity. In addition, such a system has also the advantage of easily allowing delicate manipulations of culture medium replacement. In the present study, we show the development of a laboratory scale bioprocess protocol of CHO-hTSH cell cultures on cytodex microcarriers (MCs) in a 1 L bioreactor, for the preparation of rhTSH batches in view of structure/function studies. CHO-hTSH cells were cultivated on a fetal bovine serum supplemented medium during cell growth phase. For rhTSH synthesis phase, 75% of supernatant was replaced by animal protein-free medium every 24 h. Cell cultures were monitored for agitation (rpm), temperature (A degrees C), dissolved oxygen (% DO), pH, cell concentration, MCs coverage, glucose consumption, lactate production, and rhTSH expression. The results indicate that the amount of MCs in the culture and the cell concentration at the beginning of rhTSH synthesis phase were crucial parameters for improving the final rhTSH production. By cultivating the CHO-hTSH cells with an initial cell seeding of four cells/MC on 4 g/L of MCs with a repeated fed batch mode of operation at 40 rpm, 37 A degrees C, 20% DO, and pH 7.2 and starting the rhTSH synthesis phase with 3 x 10(6) cells/mL, we were able to supply the cultures with enough glucose, to maintain low levels of lactate, and to provide high percent (similar to 80%) of fully covered MCs for a long period (5 days) and attain a high cell concentration (similar to 9 x 10(5) cells/mL). The novelty of the present study is represented by the establishment of cell culture conditions allowing us to produce similar to 1.6 mg/L of rhTSH in an already suitable degree of purity. Batches of produced rhTSH were purified and showed biological activity.

Effect of pH on citrinin and red pigments production by Monascus purpureus CCT3802

The production of red pigments and citrinin by Monascus purpureus CCT3802 was investigated in submerged batch cultures performed in two phases: in the first phase, cells were grown on glucose, at pH 4.5, 5.5 or 6.5; after glucose depletion, pH was adjusted, when necessary, to 4.5, 5.5, 6.5, 7.0, 8.0 or 8.5, for a production phase. The highest total red pigments absorbance of 11.3 U was 16 times greater than the lowest absorbance and was achieved with growth at pH 5.5, followed by production at pH 8.5, which causes an immediate reduction of the intra cellular red pigments from 75% to 17% of the total absorbance. The lowest citrinin concentration, 5.5 mg L-1, was verified in the same culture while the highest concentration, 55 mg L-1, was verified in cultures entirely carried out at pH 5.5. An alkaline medium, besides promoting intra cellular red pigments excretion, strongly represses citrinin synthesis.

Technological characterization of phosphate ore types from the Salitre Alkaline Complex, MG - Fosfertil Area

The present study was carried out on six different ore types from the Salitre Alkaline Complex aiming to determine their mineralogical composition and the major features that are relevant in the mineral processing. The P(2)O(5) grades vary from 9 to 25%. The slime content (-0, 020 mm) varies between 20 and 34% (w/w) and carries 17-22% of the P(2)O(5) content. The samples essentially consist of apatite, iron oxi-hydroxides, ilmenite, clay minerals, carbonate, quartz, pyroxene, perovskite, secondary phosphates and other minor accessory minerals. Below 0.21 mm, apatite essentially occurs in free particles showing a clean surface or a weak coating of it-on oxi-hydroxides; the highly covered apatite (not recoverable by flotation) varies from 6 to 9%. In the deslimed fraction (above 0.020 mm) more than 97% of the total phosphor content occurs as apatite; the estimated P 2 0 5 potential recovery in flotation concentration is over 90% (71-76% overall recovery).

Long-Chain Acyl-Homoserine Lactones from Methylobacterium mesophilicum: Synthesis and Absolute Configuration

The acyl-homoserine lactones (acyl-HSLs) produced by Methylobacterium mesophilicum isolated from orange trees infected with the citrus variegated chlorosis (CVC) disease have been studied, revealing the occurrence of six long-chain acyl-HSLs, i.e., the saturated homologues (S)-N-dodecanoyl (1) and (S)-N-tetradecanoyl-HSL (5), the uncommon odd-chain N-tridecanoyl-HSL (3), the new natural product (S)-N-(2E)-dodecenoyl-HSL (2), and the rare unsaturated homologues (S)-N-(7Z)-tetradecenoyl (4) and (S)-N-(2E,7Z)-tetradecadienyl-HSL (6). The absolute configurations of all HSLs were determined as 3S. Compounds 2 and 6 were synthesized for the first time. Antimicrobial assays with synthetic acyl-HSLs against Gram-positive bacterial endophytes co-isolated with M. mesophilicum from CVC-infected trees revealed low or no antibacterial activity.

Ascorbic acid metabolism in fruits: activity of enzymes involved in synthesis and degradation during ripening in mango and guava

BACKGROUND: Ascorbic acid is a very important compound for plants. It has essential functions, mainly as an antioxidant and growth regulator. Ascorbic acid biosynthesis has been extensively studied, but studies in fruits are very limited. In this work we studied the influence of five enzymes involved in synthesis (L-galactono-1,4-lactone dehydrogenase, GalLDH, EC 1.3.2.3), oxidation (ascorbate oxidase, EC 1.10.3.3, and ascorbate peroxidase, APX, EC and recycling (monodehydroascorbate reductase, EC 1.6.5.4, and dehydroascorbate reductase, DHAR, EC 1.8.5.1) on changes in ascorbic acid content during development and ripening of mangoes (Mangifera indica L. cv. Keitt) and during the ripening of white pulp guavas (Psidium guayava L. cv. Paloma). RESULTS: It was found that there was a balance between the activities of GalLDH, APX and DHAR, both in mangoes and guavas. CONCLUSIONS: Equilibrium between the enzymatic activities of synthesis, catabolism and recycling is important for the regulation of ascorbic acid content in mango and guava. These results have contributed to understanding some of the changes that occur in ascorbic acid levels during fruit ripening. (C) 2008 Society of Chemical Industry.

Synthesis of Cyclic Guanidine Intermediates of Anatoxin-a(s) in Both Racemic and Enantiomerically Pure Forms

The alkyl chain of anatoxin-a(s) (cyclic guanidines), which can be used as an intermediate in the total synthesis of anatoxin-a(s), was synthesized in both racemic and enantiomerically pure forms. These enantiomerically pure cyclic compounds can be used as chiral inductors in some reactions. The two racemic routes disclosed herein have the advantages of high overall yield and mild reaction conditions. Both routes proceed through an intermediate 2,3-diaminoacid - an important synthetic scaffold - with good yields. Furthermore, the N,N-dimethyl-2(tosylimino)imidazolidine-4-carboxamide might be obtained from 2-(tosylimino)imidazolidine-4-carboxylic acid followed by selective reduction of the carbonyl functionality. All synthesized compounds were analyzed by mass spectrometry and (1)H NMR and (13)C NMR spectroscopy.

Novel deoxy-selenylconduritols: chemoenzymatic synthesis and biological evaluation

The first synthesis of two selenyldeoxycyclitols (4-bromo-2-phenylselenyl conduritol F and 6-phenylselenylconduritol F) is reported via a chemoenzymatic enantioselective route. The key step of the synthesis is the selenolysis of a vinyl epoxide. The new compounds were evaluated for their capacity to inhibit the growth of different microorganisms using a modification of the agar diffusion technique with thin layer chromatography plates as support. (C) 2009 Elsevier Ltd. All rights reserved.