A comparative sonochemical reaction that is independent of the intensity of ultrasound and the geometry of the exposure apparatus

Sonolysis of aqueous solutions of n-alkyl anionic surfactants results in the formation of secondary carbon-centered radicals (-*CH-). The yield of -*CH- depends on the bulk surfactant concentration up to a maximum attainable radical yield (the 'plateau yield') where an increasing surfactant concentration (below the critical micelle concentration) no longer affects the -*CH- yield. In an earlier study it was found that the ratio of -*CH- detected following sonolysis of aqueous solutions of sodium pentane sulfonate (SPSo) to that of sodium dodecyl sulfate (SDS) (i.e. CH(SPSo)/CH(SDS)) depended on the frequency of sonolysis, but was independent of the ultrasound intensity, at the plateau concentrations [J.Z. Sostaric, P. Riesz, Adsorption of surfactants at the gas/solution interface of cavitation bubbles: an ultrasound intensity-independent frequency effect in sonochemistry, J. Phys. Chem. B 106 (2002) 12537-12548]. In the current study, it was found that the CH(SPSo)/CH(SDS) ratio depended only on the ultrasound frequency and did not depend on the geometry of the ultrasound exposure apparatus considered.     

Targeted damage effects of high intensity focused ultrasound (HIFU) on liver tissues of Guizhou Province miniswine

HIFU can pass through tissues and accurately damage target tissues inside organisms. This article reports on the oriented damage effects of HIFU upon miniswine internal and external liver tissues, and suggests a new conception of the 'biological focal field'. The results revealed that: (1) HIFU can be used to damage accurately liver tissues under the guide of a B-modal ultrasound device; (2) the scope of the injury is connected with sound intensity and irradiation time; and (3) the different layers of tissue through which the ultrasound has passed remain undamaged.     

Isolation, structure determination, and synthesis of galaxamide, a rare cytotoxic cyclic pentapeptide from a marine algae Galaxaura filamentosa

Galaxamide (1), a rare cyclic pentapeptide, was isolated from the marine algae Galaxaura filamentosa. A preliminary bioassay of Galaxamide showed remarkable in vitro antiproliferative activities against GRC-1 and HepG2 cell lines. The first total synthesis of the cyclic peptide was achieved for further biological evaluation.     

Estimation of physicochemical properties of ionic liquids 1-alkyl-3-methylimidazolium chloroaluminate

The density and surface tension of ionic liquids [C(2)mim][AlCl(4)] (1-ethlyl-3-methyl imidazolium chloroaluminate) and [C(6)mim][AlCl(4)] (1-hexyl-3-methylimidazolium chloroaluminate) were measured in the temperature range from 283.15 to 338.15 +/- 0.05 K. In terms of these experimental results, the estimation of physicochemical properties of 1-alkyl-3-methylimidazolium chloroaluminate ([C(n)mim][AlCl(4)], n = 1-6) was carried out. With the use of the parachor, the values of surface tension of the ILs were predicted. In terms of Glasser's theory, the standard molar entropy, lattice energy, and surface properties of the ILs were estimated. With the use of Kabo's method and Rebelo's method, the molar enthalpy of vaporization of the ILs, Delta(l)(g)H(m)(0), was predicted. According to the interstice model, the values of the thermal expansion coefficient of the ILs were also estimated. Since the magnitude order of the thermal expansion coefficient estimated by the model is in good agreement with that measured experimentally, this result means that the interstice model is reasonable.     

Study on physicochemical properties of ionic liquids based on alanine [Cnmim][Ala] (N=2,3,4,5,6)

According to Fukumoto's method, a new series of ionic liquids (ILs) based on alanine, [Cnmim][Ala] ( n=2,3,4,5,6), which comprise 1-alkyl-3-methylimidazolium cation ([Cnmim](+)) and alanine anions ([Ala] (-)), were prepared and characterized. In terms of standard addition method, the density and surface tension of amino acid ILs [Cnmim][Ala] (1-alkyl-3-methylimidazolium alpha-aminopropionic acid salt) were measured in the temperature range 293.15-343.15+/-0.05 K. The volume and surface properties of the ILs [Cnmim][Ala] were discussed. A new method of determining parachor of ionic compound was proposed and was applied to estimate the physicochemical properties of amino acid ionic liquids (AAILs): molecular volume, surface tension, molar enthalpy of vaporization, and thermal expansion coefficient. In comparison with Deetlefs's method of using neutral parachor contribution, the method proposed in this work makes smaller error in estimating properties of AAILs.     

Improved high-performance liquid chromatographic method for simultaneous determination of 12 cytotoxic caged xanthones in gamboges, a potential anticancer resin from Garcinia hanburyi

The potential anti-tumor activity of gamboges, a herbal medicine derived from Garcinia hanburyi, has increasingly gained the interest of scientist worldwide. The major components of gamboges are cytotoxic caged xanthones. In the present study, an improved HPLC method was developed to simultaneously quantify 12 caged xanthones, including three pairs of epimers and four pairs of trans-cis isomers, i.e. forbesione, isomorellic acid, morellic acid, R-30-hydroxygambogic acid, S-30-hydroxygambogic acid, isogambogenic acid, gambogenic acid, gambogellic acid, R-isogambogic acid, S-isogambogic acid, R-gambogic acid and S-gambogic acid. This method was validated to be sensitive, precise and accurate with limits of detection of 0.03-0.08 microg/mL, overall intra-day and inter-day variations less than 7.9% and overall recovery over 93.2%. The correlation coefficients (r(2)) of the calibration curves were higher than 0.995 for all analytes. The newly established method was successfully applied to reveal the difference in the chemical profiles and contents of these analytes in gamboges from different origins. It can be concluded that this method was not only an effective quality control method to ensure the safety and efficacy consistency of gamboges, but also a useful tool for screening and determining more potent cytotoxic xanthones with potential anticancer activity.     

High-impact polystyrene/polyaniline membranes for acid solution treatment by electrodialysis: preparation, evaluation, and chemical calculation

In this study different membranes were produced, aiming to evaluate their use in electrodialysis. These membranes were produced using conventional polymer (high-impact polystyrene) and polyaniline. The membrane characterization was done by FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetry (TGA). The studies of the zinc and proton extraction ionic transport through the membranes were evaluated using a three-compartment cell. The results obtained using the produced membranes were compared to the results obtained with the commercial membrane Nafion 450. It was found that a synthesized membrane can be used to recover zinc in acid media. In addition, a preliminary computational essay about the structures of PAni and CSA is presented.     

Structure-based dissection of the active site chemistry of leukotriene A4 hydrolase: implications for M1 aminopeptidases and inhibitor design

M1 aminopeptidases comprise a large family of biologically important zinc enzymes. We show that peptide turnover by the M1 prototype, leukotriene A4 hydrolase/aminopeptidase, involves a shift in substrate position associated with exchange of zinc coordinating groups, while maintaining the overall coordination geometry. The transition state is stabilized by residues conserved among M1 members and in the final reaction step, Glu-296 of the canonical zinc binding HEXXH motif shuffles a proton from the hydrolytic water to the leaving group. Tripeptide substrates bind along the conserved GXMEN motif, precisely occupying the distance between Glu-271 and Arg-563, whereas the Arg specificity is governed by a narrow S1 pocket capped with Asp-375. Our data provide detailed insights to the active site chemistry of M1 aminopeptidases and will aid in the development of novel enzyme inhibitors.     

Thermochemistry and gas-phase ion energetics of 2-hydroxy-4-methoxy-benzophenone (oxybenzone)

We have investigated the thermochemistry and ion energetics of the oxybenzone (2-hydroxy-4-methoxy-benzophenone, C14H12O3, 1H) molecule. The following parameters have been determined for this species: gas-phase enthalpy for the of neutral molecule at 298.15K, (Delta(f)H0(m)(g) = -303.5 +/- 5.1 kJ x mol-1), the intrinsic (gas-phase) acidity (GA(1H) = 1402.1 +/- 8.4 kJ x mol-1), enthalpy of formation for the oxybenzone anion (Delta(f)H0(m)(1-,g) = -402.3 +/- 9.8 kJ x mol-1). We also have obtained the enthalpy of formation of, 4-hydroxy-4'-methoxybenzophenone (Delta(f)H0(m)(g) = -275.4 +/- 10 kJ x mol-1) and 3-methoxyphenol anion (Delta(f)H0(m)(C7H7O2-,g) = -317.7 +/- 8.7 kJ x mol-1). A reliable experimental estimation of enthalpy related to intramolecular hydrogen bonding in oxybenzone has also been obtained (30.1 +/- 6.3 kJ x mol-1) and compared with our theoretical calculations at the B3LYP/6-311++G** level of theory, by means of an isodesmic reaction scheme. In addition, heat capacities, temperature, and enthalpy of fusion have been determined for this molecule by differential scanning calorimetry.