Microcionamides A and B, bioactive peptides from the philippine sponge Clathria (Thalysias) abietina

Microcionamides A (1) and B (2) have been isolated from the Philippine marine sponge Clathria (Thalysias) abietina. These new linear peptides are cyclized via a cystine moiety and have their C-terminus blocked by a 2-phenylethylenamine group. Their total structures, including absolute stereochemistry, were determined by a combination of spectral and chemical methods. Compound 1 was shown to slowly isomerize about the C-36/C-37 double bond when stored in DMSO. Microcionamides A (1) and B (2) exhibited significant cytotoxicity against the human breast tumor cells lines MCF-7 and SKBR-3 and displayed inhibitory activity against Mycobacterium tuberculosis H(37)Ra.     

Optical and Electrical Properties of Polymerizing Plasmas and Their Correlation with DLC Film Properties

Diamond-like carbon (DLC) films were grown from radiofrequency plasmas of acetylene-argon mixtures, at different excitation powers, P. The effects of this parameter on the plasma potential, electron density, electron temperature, and plasma activity were investigated using a Langmuir probe. The mean electron temperature increased from about 0.5 to about 7.0 eV while the mean electron density decreased from about 1.2 × 10⁹ to about 0.2 × 10⁹ cm^–3 as P was increased from 25 to 150 W. Both the plasma potential and the plasma activity were found to increase with increasing P. Through actinometric optical emission spectrometry, the relative concentrations of CH, [CH], and H, [H], in the discharge were mapped as a function of the applied power. A rise in [H] and a fall in [CH] with increasing P were observed and are discussed in relation to the plasma characteristics and the subimplantation model. The optical properties of the films were calculated from ultraviolet-visible spectroscopic data; the surface resistivity was measured by the two-point probe method. The optical gap, E _G, and the surface resistivity, _s, fall with increasing P. E _G and _s are in the ranges of about 2.0–1.3 eV and 10¹⁴–10¹⁶ /, respectively. The plasma power also influences the film self-bias, V _b, via a linear dependence, and the effect of V _b on ion bombardment during growth is addressed together with variation in the relative densities of sp² and sp³ bonds in the films as determined by Raman spectroscopy.     

Complexation of Hg2+ with α‐Lipoic and Dihydrolipoic Acids: Study by Differential Pulse Voltammetry on Rotating Au‐Disk Electrode and ESI‐MS

The complexation of the natural antioxidants α‐lipoic acid (ALA) and its reduced form dihydrolipoic acid (DHLA) with Hg²⁺ was investigated by a recently proposed differential pulse voltammetric (DPV) method using the rotating Au‐disk electrode. Complexation processes are proposed from the multivariate curve resolution by alternating least squares (MCR‐ALS) analysis of DPV titration data. Main complexes were both 1 : 1 Hg : ALA and Hg : DHLA, although the formation of 1 : 2 complexes can be also deduced. ALA and DHLA show different Hg²⁺‐binding patterns at different pH. Voltammetric findings are completed with the data obtained by electrospray ionization mass‐spectrometry (ESI‐MS), especially in negative mode.     

Synthesis,characterization and anticancer activity of new palladacycles derived from chiral α‐diimines

Optically pure α‐diimines quantitatively obtained in solvent‐free conditions starting from 2,3‐butanedione and (S)‐(?)‐1‐phenylethylamine and (S)‐(?)‐1‐(4‐methylphenyl)ethylamine, respectively, yielded the new chiral mono‐Pd complexes 2a–b, which have been partly characterized by IR, ¹H‐ and ¹³C‐NMR spectroscopies along with MS‐FAB⁺ spectrometry. The crystal and molecular structure for palladacycle 2a has been fully confirmed by single‐crystal X‐ray studies. Studies in vitro of 2a–b have displayed growth inhibition against different classes of cancer: leukemia (K‐562 CML), colon cancer (HCT‐15), breast cancer (MCF‐7), central nervous system (U‐251 Glio) and prostate cancer (PC‐3) cell lines. Copyright © 2009 John Wiley & Sons, Ltd.     

Nir-chemical imaging study of acetylsalicylic acid in commercial tablets

Near Infrared Chemical Imaging (NIR-CI) is demonstrating an increasing interest in pharmaceutical research since it meets the challenging analytical needs of pharmaceutical quality and may serve as a versatile adjunct to conventional NIR spectroscopy in many fields.The direct analysis of samples by using hyperspectral imaging techniques, which provide a NIR spectrum in each pixel of the image, generates a big amount of information from one sample. Focusing the interest in pharmaceutical research, several chemometric algorithms are demonstrating their usefulness extracting the relevant information (i.e. quantitative determination of the component in one sample) in tablets with only one sample and without damaging it.In this work, a quantitative method to analyze different commercial Acetylsalicylic acid tablets is proposed by using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) method to the hyperspectral image and without any previous calibration model. For this purpose, a large concentration range of active pharmaceutical ingredient (ASA, Acetylsalicylic acid in this work), between 82% and 12%, was covered depending on the manufacturer. MCR-ALS allowed obtaining a concentration maps for acetylsalicylic acid and therefore, consequent analysis of the ASA distribution in the tablet was developed by using the histograms of the distribution of concentration.Results certified the good distribution of ASA despite the different origins of the tablets. Moreover, the obtained values of concentration showed a very good concordance with the nominal value of ASA. As a matter of fact, the quality of the results demonstrated the useful of encompassing NIR-CI techniques with MCR-ALS and, consequently, the well development on the production of Acetylsalicylic acid tablets.     

Application of near infrared spectroscopy and multivariate data analysis for the evaluation of glue lines of untreated and copper azole treated laminated timber before and after ageing

The necessity for inspection and assessment of glued laminated timber structures in service has raised interest in the evaluation of the glue lines. Glue line spectra were analysed and are discussed in detail with respect to spectral contributions from the adhesive, the hardener, the wood lamella below the adhesive, the curing temperature as well as ageing-related spectral changes. The combination of near infrared (NIR) spectroscopy and principal component analysis (PCA) allowed distinguishing between aged and non-aged samples and different copper azole preservative treatment levels of phenol-resorcinol-formaldehyde (PRF) glue lines. NIR-based partial least squares (PLS) regression modelling was performed for the glue line shear strength and for the curing temperature. These findings show that NIR spectroscopy is a fast and useful technique to evaluate the degradation on the PRF glue lines of untreated and copper azole treated laminated timber.     

Predicting adsorption isotherms of asphaltenes in porous materials

In this paper we present a molecular thermodynamics approach for the modeling of adsorption isotherms of asphaltenes adsorbed on Berea sandstone, Bedford limestone and dolomite rock, using a model for bulk asphaltenes precipitation and a quasi-two-dimensional approach for confined fluids [E. Buenrostro-González, C. Lira-Galeana, A. Gil-Villegas, J. Wu, AIChE J., 50 (2004) 2552–2570; A. Martínez, M. Castro, C. McCabe A. Gil-Villegas, J. Chem. Phys. 126 (2007) 074707, respectively], both based on the Statistical Associating Fluid Theory for Potentials of Variable Range [A. Gil-Villegas, A. Galindo, P.J. Whitehead, S.J. Mills, G. Jackson, A.N. Burgess, J. Chem. Phys. 106 (1997) 4168–4186]. The theory is applied to model adsorption isotherms from experimental data of asphaltenes extracted from a dead sample of heavy crude oil from a Mexican reservoir. The theoretical results give the right Langmuir Type II adsorption isotherms observed experimentally. The model requires the determination of ten molecular parameters related to the size of the particles and the square-well potentials used to describe the particle–surface and particle–particle interactions at the bulk and adsorbed phases. Nine parameters are taken from previous published results about the behavior of asphaltenes in bulk phases and the adsorption of several molecular fluids onto activated carbon and graphite surfaces. The remaining parameter, the energy strength of the particle–surface interaction, is adjusted to reproduce the experimental data, obtaining values that are consistent with Molecular Mechanics calculations for asphaltenes adsorbed on different surfaces and solutions. Although the agreement between theory and experiments shows some deviations at low bulk concentrations, the model reproduces adsorption data at high concentrations where other semi-empirical approaches fail.     

Ferrocenyl‐Ended Thieno–Vinylene Oligomers: Donor–Acceptor Polarization and Mixed‐Valence Properties with Emphasis on the Raman Mapping of Localized‐to‐Delocalized Transitions

What's your role? New oligothiophene–vinylene compounds have been synthesized to study the role of the conjugated chain in two different cases (see scheme; MV=mixed valence). The electronic and molecular structures were analyzed by means of electronic, X‐ray photoelectron, and Raman spectroscopy, together with thermo spectroscopy, electrochemistry, and DFT calculations.

     

Photocatalytic behavior of α-Bi2Mo3O12 prepared by the Pechini method: degradation of organic dyes under visible-light irradiation

Nanoparticles of α-Bi₂Mo₃O₁₂ were prepared by the Pechini method. The process of formation of the bismuth molybdate was followed by simultaneous thermogravimetric and differential thermal analysis (TGA/DTA). Different samples of α-Bi₂Mo₃O₁₂ were obtained at 400, 450, and 500 °C, and characterized by X-ray powder diffraction (XRD), nitrogen physisorption (BET), and scanning electron microscopy (SEM). When observed by SEM, the morphology of the sample obtained at the lowest temperature consisted of semi-spherical particles with an average diameter of 150 nm. On the other hand, the highest calcination temperature led to the formation of sintered particles of 500–600 nm. The photocatalytic activity of α-Bi₂Mo₃O₁₂ was tested by photodegradation of the organic dyes rhodamine B (rhB) and indigo carmine (IC) under visible-light irradiation. The bismuth molybdate nanoparticles were able to bleach aqueous solutions of both organic dyes. The sample obtained at 400 °C was the best photocatalyst with half-lives, t _1/2, of 108 and 154 min for rhB and IC, respectively.     

Synthesis and characterization of WO3 nanoparticles prepared by the precipitation method: Evaluation of photocatalytic activity under vis-irradiation

WO₃ nanoparticles were synthesized by the precipitation method varying the time employed in the formation of their precursor in aqueous media and the calcination temperature. The WO₃ crystallization process and morphology of the synthesized samples were followed by the XRD, TEM and SEM techniques. The effects of the calcination temperature on the surface area and optical properties of the WO₃ nanoparticles were also investigated. Nanoparticles with morphologies such as square and rectangular plates and ovoid forms were observed for the different experimental conditions. WO₃ nanoparticles with different morphologies were tested for the photocatalytic degradation of organic dyes. In general, the photocatalysts showed a capacity to bleach the dye solution in the following sequence: indigo carmine (IC) > rhodamine B (rhB) > congo red (CR). The extent of mineralization was determined by means of total organic carbon (TOC) measurements, which showed a satisfactory TOC reduction (93%, within 75 h) only for IC. This value was even better than the one concerning the P-25 Degussa reference.