Salting-in effect of ionic liquids on poly(N-vinylimidazole) hydrogels

This work attempts to study the interaction of two ionic liquids (1-ethyl-3-methylimidazolium tosylate and 1-hexyl-3-methylimidazolium chloride) with chemically crosslinked poly(N-vinylimidazole) in aqueous media, and to compare it with that of NaCl, a typical salting-out electrolyte. The three salts show a salting-in effect whose intensity was measured on the basis of the decrease of the polymer–solvent interaction parameter and the increase of swelling with increasing ionic strength. It was thus found that the salting-in effect is the same for the two salts with the same anion (chloride), while the intensity of the salting-in effect exerted by the tosylate ionic liquid is larger. The coefficient of selective sorption, which expresses the salt excess inside the swollen gel with respect to the external solution was determined by comparing the initial and equilibrium compositions of the immersion bath. These results are discussed in terms of the hydrophobic character of the ions involved.     

Aromatic Nucleophilic Substitution: The Reaction of Sodium 2,2,2-Trifluoroethoxide with Chlorobenzonitriles in HMPA

The preparation¹ of fluorinated compounds continues to be of significant interest to organic chemists due to their diverse and important application as polymers, blood substitutes, pharmaceuticals and pesticides. Considerable attention has been directed to the formation of fluoroalkoxy benzenes with the majority of the synthetic routes involving the reaction of an electrophilic haloalkyl fluoride with a nucleophilic phenol derivative^1,2. In a somewhat related procedure, Mendel³ has prepared ortho-2,2,2-trifluoroethoxy methyl benzoate by reacting ortho-hydroxy methyl benzoate with 2,2,2-trifluoroethyl trifluoromethylsulfonate in a potassium carbonate/acetone mixture.     

Evaluation of thermal stability and parameters of dissolution of nifedipine crystals

Nifedipine is a calcium channel blocker as well as a powerful vasodilator used to treat ischemic heart disease and hypertension. Its photosensitivity and very low solubility in water have been widely acknowledged as important properties deserving improvements. The main thrust of this study is to characterize the nature and the solid-state of nifedipine crystals obtained using different solvents as well as assess the stability by thermal methods (TG and DSC) and crystals structure by means of spectroscopic techniques (MID FTIR and XRD) and assess the dissolution parameters for such crystals. The calculated kinetic parameters activation energy (E _a = 123.3 kJ mol^?1 ± 0.1), the factor frequency (A = 25.93 ± 0.9 min^?1), and the reaction order (n = 0.2) of the main stage of thermal decomposition of nifedipine raw material were performed according to the Ozawa model. The data showed a zero-order kinetic behavior for all crystals despite the different values of E _a and A. The dissolution profiles were obtained for such crystals in three dissolution media with different pH values. After 1 h of dissolution, the higher amount of nifedipine dissolved was observed for crystals obtained in isopropyl alcohol (52.5 %, pH 4.5), followed by those in chloroform (48.1 %, pH 1.2) and subsequently in acetone (32.5 %, pH 6.8). Results showed different thermal stabilities and significant variations in the solubility of the crystals.     

Simple and rapid CE-UV method for the assessment of trail pheromone compounds of leaf-cutting ants' venom glands

Leaf-cutting ants cause large losses in several crops around the world. In the ant species Atta sexdens, each colony comprises up to 5 million individuals. In order to keep a close connection among such a large number of individuals, an efficient chemical communication system is necessary. Among other different substances, these animals use alkylpyrazines to mark their trails and to guide ant workers from the nest to their sources of food. In this study, CE-UV was used to apply a method for qualitative analysis of venom gland components of leaf-cutting ants. Mobility of these compounds proved to be a function of the ionization capability of these bases as well as their volumes. Migration order was thoroughly explained in terms of such parameters. The best analysis conditions were achieved with a BGE composed by 0.8% formic acid plus 20% methanol in water, hydrodynamic injection, and application of external pressure. Such analysis conditions may be easily applied in CE-MS analyses as well. CE-UV analyses proved to be as adequate as GC to analyze such compounds due to system detectability (LD ? 0.005?mmol/L), separation efficiency (from 5.07×10(4) to 1.23×10(5) theoretical plates), and resolution (minimum of 2.35). In addition, analysis time was ca. 15 min, which shows another advantage of CE analysis when compared with GC. Although the analytes are found in concentrations as low as 50 ng/venom glands, four putative pyrazine ring moiety substances could be detected in real samples, due to sample stacking and use of a capillary with extended detection cell.     

Infrared (810 nm) low-level laser therapy in rat achilles tendinitis: a consistent alternative to drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used and can reduce musculoskeletal pain in spite of the cost of adverse reactions like gastrointestinal ulcers or cardiovascular events. The current study investigates if a safer treatment such as low-level laser therapy (LLLT) could reduce tendinitis inflammation, and whether a possible pathway could be through inhibition of either of the two-cyclooxygenase (COX) isoforms in inflammation. Wistar rats (six animals per group) were injected with saline (control) or collagenase in their Achilles tendons. Then, we treated them with three different doses of IR LLLT (810 nm; 100 mW; 10 s, 30 s and 60 s; 3.57 W cm(-2); 1 J, 3 J, 6 J) at the sites of the injections, or intramuscular diclofenac, a nonselective COX inhibitor/NSAID. We found that LLLT dose of 3 J significantly reduced inflammation through less COX-2-derived gene expression and PGE(2) production, and less edema formation compared to nonirradiated controls. Diclofenac controls exhibited significantly lower PGE(2) cytokine levels at 6 h than collagenase control, but COX isoform 1-derived gene expression and cytokine PGE(2) levels were not affected by treatments. As LLLT seems to act on inflammation through a selective inhibition of the COX-2 isoform in collagenase-induced tendinitis, LLLT may have potential to become a new and safer nondrug alternative to coxibs.     

Synthesis and structure of new aryltellurenyl halides derived from (dmpTe)2 (dmp = 2,6-dimethoxyphenyl)

[RTeTeR] (R = dmp = 2,6-dimethoxyphenyl) (1) reacts with bromine to give [RTeTe(Br)₂R] (2) and [RTeBr₃] (3), and with SOCl₂ to yield [RTeTe(Cl)₂R] (5) and [RTeCl₃] (6). The recrystallization of compound 3 in acetone produces [RTeBr₂(CH₂-C(O)-CH₃)] (4). The hydrolysis of 2 in aqueous ammonia and methanol containing media affords the methoxy/oxo-derivative [RTe(μ-O)(OCH₃)]₂ (7). All the title compounds were obtained with good yields, and strong Te?O_(methoxy), as well as Te?X (X = Br, Cl) secondary interactions, support the distorted octahedral configurations shown mostly in the polymeric compounds 3, 4, 5 and 6. Complexes 2 and 5 close the series of compounds with the structure [RTeTe(X)₂R] (X = Cl, Br, I), started earlier with [RTeTe(I)₂R].     

Unexpected influence of stereochemistry on the cytotoxicity of highly efficient Ti(IV) salan complexes: new mechanistic insights

The effect of stereochemistry on the cytotoxicity of highly active and hydrolytically stable N-methylated Ti(IV) salan complexes is reported. Four bis(isopropoxo) complexes incorporating N-methylated salan ligands with different aromatic substitution patterns have been prepared in racemic and optically active forms for the first time by ligand-to-metal chiral induction from trans-diaminocyclohexyl-based chiral ligands. The configuration of the metal center that derives from that of the ligand has an enormous influence on cytotoxicity, with the racemic mixture mostly being more active than the single enantiomers that are of either similar or different activity. This implies that the active species is a salan-bound heterochiral polynuclear compound, interacting with a chiral target. Four additional complexes of achiral salan and chiral labile sec-butoxo ligands, analyzed as racemic and as homochiral, revealed no influence of stereochemistry, supporting early dissociation of the labile ligands to give the polynuclear products.     

Different ortho and para electronic effects on hydrolysis and cytotoxicity of diamino bis(phenolato) "salan" Ti(IV) complexes

Bis(isopropoxo) Ti(IV) complexes of diamino bis(phenolato) "salan" ligands were prepared, their hydrolysis in 1:9 water/THF solutions was investigated, and their cytotoxicity toward colon HT-29 and ovarian OVCAR-1 cells was measured. In particular, electronic effects at positions ortho and para to the binding phenolato unit were analyzed. We found that para substituents of different electronic features, including Me, Cl, OMe, and NO(2), have very little influence on hydrolysis rate, and all para-substituted ortho-H complexes hydrolyze slowly to give O-bridged clusters with a t(1/2) of 1-2 h for isopropoxo release. Consequently, no clear cytotoxicity pattern is observed as well, where the largest influence of para substituents appears to be of a steric nature. These complexes exhibit IC(50) values of 2-18 μM toward the cells analyzed, with activity which is mostly higher than those of Cp(2)TiCl(2), (bzac)(2)Ti(OiPr)(2) and cisplatin. On the contrary, major electronic effects are observed for substituents at the ortho position, with an influence that exceeds even that of steric hindrance. Ortho-chloro or -bromo substituted compounds possess extremely high hydrolytic stability where no major isopropoxo release as isopropanol occurs for days. In accordance, very high cytotoxicity toward colon and ovarian cells is observed for ortho-Cl and -Br complexes, with IC(50) values of 1-8 μM, where the most cytotoxic complexes are the ortho-Cl-para-Me and ortho-Br-para-Me derivatives. In this series of ortho-substituted complexes, the halogen radius is of lesser influence both on hydrolysis and on cytotoxicity, while OMe substituents do not impose similar effect of hydrolytic stability and cytotoxicity enhancement. Therefore, hydrolytic stability and cytotoxic activity are clearly intertwined, and thus this family of readily available Ti(IV) salan complexes exhibiting both features in an enhanced manner is highly attractive for further exploration.     

Differential expression of myogenic regulatory factor MyoD in pacu skeletal muscle (Piaractus mesopotamicus Holmberg 1887: Serrasalminae, Characidae, Teleostei) during juvenile and adult growth phases

Skeletal muscle is the edible part of the fish. It grows by hypertrophy and hyperplasia, events regulated by differential expression of myogenic regulatory factors (MRFs). The study of muscle growth mechanisms in fish is very important in fish farming development. Pacu (Piaractus mesopotamicus) is one of the most important food species farmed in Brazil and has been extensively used in Brazilian aquaculture programs. The aim of this study was to analyze hyperplasia and hypertrophy and the MRF MyoD expression pattern in skeletal muscle of pacu (P. mesopotamicus) during juvenile and adult growth stages. Juvenile (n = 5) and adult (n = 5) fish were anaesthetized, sacrificed, and weight (g) and total length (cm) determined. White dorsal region muscle samples were collected and immersed in liquid nitrogen. Transverse sections (10 μm thick) were stained with Haematoxilin–Eosin (HE) for morphological and morphometric analysis. Smallest fiber diameter from 100 muscle fibers per animal was calculated in each growth phase. These fibers were grouped into three classes (<20, 20–50, and >50 μm) to evaluate hypertrophy and hyperplasia in white skeletal muscle. MyoD gene expression was determined by semi-quantitative RT-PCR. PCR products were cloned and sequenced. Juvenile and adult pacu skeletal muscle had similar morphology. The large number of <20 μm diameter muscle fibers observed in juvenile fish confirms active hyperplasia. In adult fish, most fibers were over 50 μm diameter and denote more intense muscle fiber hypertrophy. The MyoD mRNA level in juveniles was higher than in adults. A consensus partial sequence for MyoD gene (338 base pairs) was obtained. The Pacu MyoD nucleotide sequence displayed high similarity among several vertebrates, including teleosts. The differential MyoD gene expression observed in pacu white muscle is possibly related to differences in growth patterns during the phases analyzed, with hyperplasia predominant in juveniles and hypertrophy in adult fish. These results should provide a foundation for understanding the molecular control of skeletal muscle growth in economically important Brazilian species, with a view to improving production quality.     

Temporally controlled modulation of antihydrogen production and the temperature scaling of antiproton-positron recombination

We demonstrate temporally controlled modulation of cold antihydrogen production by periodic RF heating of a positron plasma during antiproton-positron mixing in a Penning trap. Our observations have established a pulsed source of atomic antimatter, with a rise time of about 1 s, and a pulse length ranging from 3 to 100 s. Time-sensitive antihydrogen detection and positron plasma diagnostics, both capabilities of the ATHENA apparatus, allowed detailed studies of the pulsing behavior, which in turn gave information on the dependence of the antihydrogen production process on the positron temperature T. Our data are consistent with power law scaling T (-1.1+/-0.5) for the production rate in the high temperature regime from approximately 100 meV up to 1.5 eV. This is not in accord with the behavior accepted for conventional three-body recombination.