Characterisation of Xerogels Derived from Sucrose Templated Sol-Gel Synthesis

This work presents the results of the nanostructural characterisation of the effect of sucrose as a template added to a sol derived from a tetraethoxysilane acid catalysed process. By increasing the sucrose template ratio, N₂ adsorption isotherms showed that the xerogel samples changed from a micropore to a mesopore nanostructure as evidenced by the formation of hysteresis at 0.5 partial pressure. In turn, this led to a direct increase in surface areas, pore volumes and average pore sizes. Sucrose has two molecular components of the same molecular weight: D-fructose and D-glucose. D-fructose resulted in the formation of higher pore volumes and pore sizes, while D-glucose formed higher surface area xerogels. Depending of the template ratio employed in the xerogel synthesis, average pore radius ranged from 8.8 to 26 Å, while surface areas increased by over two fold up to 750 m²·g^?1. However, pore volumes increased by as much as six fold, from 0.15 to almost 1 cm³·g^?1.     

Syntheses,crystal structures and electron paramagnetic resonance studies of Co- and Mn-coordination polymers with the twisted ligand di(4-pyridyl)disulfide in double bridge fashion

Four coordination polymers, {[Co₂(4-DPSS)₄(DMF)₄](ClO₄)₄}_n (1), {[Mn₂(4-DPSS)₄(DMF)₄](ClO₄)₄}_n (2), {[Co(4-DPSS)₂(H₂O)(NO₃)]NO₃·3H₂O}_n (3) and [Co(4-DPSS)₂(NCS)₂]_n (4) have been synthesized to study the reactivity of cobalt(II) and manganese(II) salts (perchlorate, thiocyanate and nitrate) with the flexible ligand di(4-pyridyl)disulfide (4-DPSS). These compounds have repeated rhomboidal structures in which the di(4-pyridyl)disulfide ligands coordinate the metal centers in a double bridged fashion. Each double chain and the metallocycle cavities are chiral and contain either the M- or the P-enantiomeric forms of 4-DPSS and are independent on recrystallization solvents or the metallic precursors. The crystal packing of these coordination polymers reveals that, in all cases, weak interactions such as classical and non-classical hydrogen bonds, as well as S?S interactions, connect the polymeric chains to increase the dimensionality of the network. Low temperature electron paramagnetic resonance (EPR) measurements on powdered samples show that the transition-metal ions, Co (II) and Mn (II) ions, are in the high spin states S = 3/2 and 5/2, respectively, and adopt octahedral geometry in case of compounds 1, 2 and 3, and rhombic environment in case of 4.     

<em>In Vitro </em>and <em>in </em><em>Vivo</em> Antitumor Effect of Trachylobane-360, a Diterpene from<em> Xylopia langsdorffiana</em>

Trachylobane-360 (ent-7α-acetoxytrachyloban-18-oic acid) was isolated from Xylopia langsdorffiana. Studies have shown that it has weak cytotoxic activity against tumor and non-tumor cells. This study investigated the in vitro and in vivo antitumor effects of trachylobane-360, as well as its cytotoxicity in mouse erythrocytes. In order to evaluate the in vivo toxicological aspects related to trachylobane-360 administration, hematological, biochemical and histopathological analyses of the treated animals were performed. The compound exhibited a concentration-dependent effect in inducing hemolysis with HC₅₀ of 273.6 μM, and a moderate in vitro concentration-dependent inhibitory effect on the proliferation of sarcoma 180 cells with IC₅₀ values of 150.8 μM and 150.4 μM, evaluated by the trypan blue exclusion test and MTT reduction assay, respectively. The in vivo inhibition rates of sarcoma 180 tumor development were 45.60, 71.99 and 80.06% at doses of 12.5 and 25 mg/kg of trachylobane-360 and 25 mg/kg of 5-FU, respectively. Biochemical parameters were not altered. Leukopenia was observed after 5-FU treatment, but this effect was not seen with trachylobane-360 treatment. The histopathological analysis of liver and kidney showed that both organs were mildly affected by trachylobane-360 treatment. Trachylobane-360 showed no immunosuppressive effect. In conclusion, these data reinforce the anticancer potential of this natural diterpene.     

Photobiomodulation Enhances Cisplatin Cytotoxicity in a Culture Model with Oral Cell Lineages

Cisplatin plays a central role in cancer chemotherapy, but resistance to this drug remains a major obstacle in treatment. Drawbacks related to cisplatin failure may be associated with cell energy metabolism. This study investigated whether photobiomodulation (PBM) can potentiate the effects of cisplatin on keratinocytes (HaCat) and cancer cells (SCC25 and HN12). Cells were treated with laser (GaAlAs; 660 nm; 60 mW; 0.33 J; 2.14 W cm⁻²; 11.7 J cm⁻² and 6 s) and cisplatin (7.8 μg mL⁻¹) to evaluate cell viability, Ki-67, VEGF, TGF-β1, EGF expression and ROS production. Observations were validated in the SCC25 cell lineage, where the type of cell death (necrosis/apoptosis) and the amount of ATP were assessed. Cell lineages showed increased sensitivity to cisplatin associated with PBM (Cis-PBM). Ki-67 was augmented in all cell lineages treated with Cis-PBM when compared to cisplatin alone (Cis). Cis or Cis-PBM significantly decreased VEGF expression in cancer cells, while no changes were seen in the expression of TGF-β1 or EGF compared to control. ROS levels were similar in the Cis and Cis-PBM groups. Cells treated with Cis-PBM died by apoptosis, leading to greater consumption of ATP. These observations suggest that PBM may potentiate the effects of cisplatin, leading to increased drug cytotoxicity and enhanced cell death.     

Synthesis of Mercaptobenzothiazole and Mercaptobenzimidazole Condensed with Inositol Derivatives

This work describes the synthesis of inositol derivatives condensed with 2‐mercaptobenzothiazole or 2‐mercaptobenzimidazole, potential antimicrobial agents. These compounds were prepared by ring opening of epoxide intermediate (2S,3R‐epoxy‐1‐O‐methyl‐ l ‐chiro‐inositol and 2R,3S‐epoxy‐1‐O‐methyl‐ l ‐chiro‐inositol), which were obtained from l ‐quebrachitol (1‐O‐methyl‐chiro‐inositol). Microwave irradiation was used to promote the condensation reaction.     

Structural Insights into the Molecular Recognition Mechanism of the Cancer and Pathogenic Epitope,LacdiNAc by Immune-Related Lectins

Interactions of glycan-specific epitopes to human lectin receptors represent novel immune checkpoints for investigating cancer and infection diseases. By employing a multidisciplinary approach that combines isothermal titration calorimetry, NMR spectroscopy, molecular dynamics simulations, and X-ray crystallography, we investigated the molecular determinants that govern the recognition of the tumour and pathogenic glycobiomarker LacdiNAc (GalNAcβ1-4GlcNAc, LDN), including their comparison with the ubiquitous LacNAc epitope (Galβ1-4GlcNAc, LN), by two human immune-related lectins, galectin-3 (hGal-3) and the macrophage galactose C-type lectin (hMGL). A different mechanism of binding and interactions was observed for the hGal-3/LDN and hMGL/LDN complexes, which explains the remarkable difference in the binding specificity of LDN and LN by these two lectins. The new structural clues reported herein are fundamental for the chemical design of mimetics targeting hGal-3/hMGL recognition process.     

keV right-handed neutrinos from type II seesaw mechanism in a 3-3-1 model

We adapt the type II seesaw mechanism to the framework of the 3-3-1 model with right-handed neutrinos. We emphasize that the mechanism is capable of generating small masses for the left-handed and right-handed neutrinos and the structure of the model allows that both masses arise from the same Yukawa coupling. For typical values of the free parameters of the model we may obtain at least one right-handed neutrino with mass in the keV range. Right-handed neutrino with mass in this range is a viable candidate for the warm component of the dark matter existent in the universe.     

Ultrasonic-based protein quantitation by (18) O-labeling: optimization and comparison between different procedures

Herein we report results regarding the optimization and comparison between different ultrasonic‐based procedures for protein quantitation by the direct ¹⁸O‐labeling approach. The labeling procedure was evaluated using different proteins, different ultrasonic devices and different reaction times: from 30 s to 10 min with the ultrasonic probe and from 30 s to 30 min with the sonoreactor. Variables such as the enzyme‐to‐protein ratio and protein concentration were also assessed. The results show that it is possible to accelerate the labeling reaction from 12 h to only 15 min with the sonoreactor without compromising the labeling efficiency. A larger variation in the double labeling yield was obtained among the different peptides, but the values for the smaller peptides are similar to the ones achieved with the classic methodology. These findings were further confirmed by labeling a complex protein mixture from human plasma. It was also found that the labeling reaction is affected by the sample concentration, even when performed with the classic overnight procedure. Copyright © 2010 John Wiley & Sons, Ltd.     

Bioadsorption and ion exchange of Cr3+ and Pb2+ solutions with algae

Heavy metals can be removed from effluents and recovered using physico-chemical mechanisms as biosorption processes. In this work “Arribada” seaweed biomass was employed to assess its biosorptive capacity for the chromium (Cr³⁺) and lead (Pb²⁺) cations that usually are present in waste waters of plating industries. Equilibrium and kinetic experiments were conducted in a mixed reactor on a batch basis. Biosorption equilibrium and fluid-solid mass transfer constants data were analyzed through the concept of ion exchange sorption isotherm. The respective equilibrium exchange constants (K _eqCr=173.42, K _eqPb=58.86) and volumetric mass transfer coefficients ((k _mCr a)′=1.13×10⁻³ s⁻¹, (k _mPb a)′=0.89×10⁻³ s⁻¹) were employed for the dynamic analysis of Cr and Pb sorption in a fixed-bed flow-through sorption column. The breakthrough curves obtained for both metals were compared with the predicted values by the heterogeneous model (K _eqCr=171.29, K _eqPb=60.14; k _mCr a=7.81×10⁻² s⁻¹, k _mPb a=2.43×10⁻² s⁻¹), taking into account the mass transfer process. The results suggest that these algae may be employed in a metal removal/recovery process at low cost. An erratum to this article can be found at     

Characterization of hybrid organic and inorganic functionalised membranes for proton conduction

Titanium zirconium phosphate and organic polymer hybrid (poly-vinyl alcohol, (3-glycidoxypropyl)-trimethoxysilane and ethylene glycol) based membranes were investigated for their potential application as proton conductors. The hybrid materials were characterized by XRD, FTIR, SEM, TGA and impedance spectroscopy analysis. It was found that embedding of functionalised inorganic particles (TiZrP) into composite polymer matrix allowed for some crystallinity formation, and cross-linking of hydroxyl groups during annealing or reactions within the organic and inorganic phases during synthesis. A complex structure was formed, as many FTIR peaks were masked by more defined peaks assigned to P–O–R bonds. The high concentration of phosphorus in the TiZrP (1:1:9 molar ratio) samples resulted in more hydrophilic particles. This was further reflected in the hybrid membranes as the water losses increased from 13 to 25 wt.% as a function of the TiZrP content changing from 10 to 50 wt.% in the final hybrid membrane, respectively. As a result, proton conductivity increased by two to three orders of magnitude from blank (organic phase only) membranes (2.61 × 10^− 5 S cm^− 1) to TiZrP hybrid membrane (2.41 × 10^− 2 S cm^− 1) at 20 °C. Proton conduction changed as a function of temperature and the Ti1Zr1P9 particles content, mainly attributed to the membrane ability to retain water, thus complying with the Grotthus mechanism.