A Multicomponent Model of Chromophoric Dissolved Organic Matter Photobleaching¶§

Light absorption by chromophoric dissolved organic matter (CDOM) plays a number of roles in natural waters, including both control of the underwater light field and the initiation of many photochemical reactions. A multicomponent analysis was used to describe the effects of UV and visible radiation on the optical absorption spectra of two natural water samples, a Suwannee River fulvic acid standard (SRFA) and a Delaware Bay water sample. This analysis used a constrained minimization technique to fit independent spectral components to the observed bleaching behavior of the water samples under monochromatic irradiation. Spectra derived from these fits were used to predict the bleaching behavior of both samples under polychromatic irradiation (λ< 320 nm). This approach reproduces the kinetics and spectral behavior of polychromatic photobleaching very well at times <48 h, but underpredicts the bleaching at longer time periods.     

TG and DSC investigation of gallstone samples collected from patients submitted to cholecystectomy

In the present work are performed the TG and DSC study of gallstone samples collected from patients submitted to cholecystectomy at the Hospital Universitário Onofre Lopes of Universidade Federal do Rio Grande do Norte, in Natal, Rio Grande do Norte State, Brazil. The gallstone samples were characterized by elemental analysis and infrared spectroscopy. Standard cholesterol was used for all analysis as comparison with the gallstones. Is verified that cholesterol is the main chemical component of all studied gallstone samples. The thermoanalytical study was performed on air and nitrogen atmospheres. The presence of cholesterol as the main chemical component of all gallstone samples is confirmed by TG and DSC results.     

Rheological techniques for the determination of the crystallization kinetics of a polypropylene–EPR copolymer

In this article, we show that the crystallization behaviour of a rubber-filled polypropylene, under isothermal conditions, can be monitored by means of parallel plate rheometry and differential scanning calorimetry. Data collected with different instruments can be compared only after performance of accurate temperature calibration. The complex modulus as obtained from dynamic mechanical measurements can be related to the crystalline content by use of appropriate mathematical relationships. An empirical power law model is used to correlate the crystalline content to the rheological function. Excellent agreement between rheological and calorimetric data is found. Furthermore, it is shown that rheology can be used to achieve additional information on the structural evolution of the crystallizing system.     

A systematic shift in the electronic spectra of substituted benzene molecules trapped in helium nanodroplets

Electronic spectra (S1<--S0) have been recorded from five separate substituted benzene derivatives trapped in helium nanodroplets. Each member of the series is found to exhibit a blueshift with respect to the equivalent transition in the gas phase. Taken together with previous results for benzene, the observed shifts show a remarkably good correlation with changes in electron density that occur within each of the aromatic rings as a result of electronic excitation.     

19F, (1)H-HOESY and PGSE NMR studies of neutral trinuclear complexes of Au(I) and Hg(II): evidence for acid-base stacking in solution

By combining the information from 19F, 1H-HOESY and PGSE NMR methodologies, unprecedented direct evidence has been obtained for the formation of supramolecular assemblies in solution between the trinuclear cyclic AuI basic compounds ([Au(mu-C2,N3-bzim)]3 (bzim = 1-benzylimidazolate), 1, and [Au(mu-C,N-C(OEt)=N-p-C6H4-CH3)]3, 2, on one hand, and the trinuclear cyclic HgII acid complex [Hg(mu-C,C-C6F4)]3, 3, on the other hand. HOESY experiments indicate that a stacking similar to that observed in the solid state occurs. PGSE studies demonstrate the presence of an equilibrium between the free trinuclear entities and adduct A in the case of 2/3 admixtures (see Sketch) while for 1/3 admixtures, adducts A and B are mainly present in solution.     

Influence of olive (cv Grignano) fruit ripening and oil extraction under different nitrogen regimes on volatile organic compound emissions studied by PTR-MS technique

Volatile organic compounds of extra virgin olive oils obtained from the local Italian cultivar Grignano were measured by proton transfer reaction–mass spectrometry (PTR-MS). Oils were extracted by olives harvested at different ripening stages across veraison, performing each extraction step and the whole extraction process in nitrogen atmosphere to observe the changes in the volatile profiles of the oils. Principal component analysis carried out on the full spectral signature of the PTR-MS measurements showed that the stage of ripening has a stronger effect on the global definition of volatile profiles than the use of nitrogen during oil extraction. The fingerprint-like chemical information provided by the spectra were used to construct a heat map, which allowed the dynamical representation of the multivariate nature of mass evolution during the ripening process. This provided the first evidence that some groups of volatile organic compounds displayed a time course of regulation with coordinated increasing or decreasing trends in association with specific stages of fruit ripening.     

Functionalization of Biodegradable Polyester for Tissue Engineering Applications

Summary: Chemical modification of polymer surface may potentially be used to create smart materials that can guide cellular adhesion, proliferation and maintenance of specific expression of molecules. The microbial polyester poly (3-hydroxybutyrate) (PHB) has been attracted attention as promising material for applications in tissue engineering. In this work, a wet-chemical method, base ethylenediamine aminolysis, was performed to improve the adhesion of chondrocytes isolated from human articular cartilage to PHB films. The effects of chemical treatment on PHB films was evaluated by following changes in morphology and surface chemical composition using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. While the effect on cells morphology was studied by scanning electron microscopy (SEM). The treatment with ethylenediamine did not change significantly the morphology of the structures of PHB films surface. However, the roughness of the aminolyzed films was slightly higher. The introduction of nitrogen-containing groups was confirmed by XPS. In vitro experiments indicated that the surface modification did not have toxic effects in cells, since they could adhere and proliferate on modified PHB films. It was observed that long-time treatment improved ability of PHB films to support cell growth, which could be accounted to physicochemical and topological effects.     

Intramolecular diels-alder reactions of the furan diene: substituent and solvent effects

An internal Diels-Alder reaction, using furan as the diene component, formed a highly functionalized 5-membered carbocyclic ring in excellent yield. Solvent and substituent effects of this reaction were examined.     

The Glucosamine-derivative NAPA Suppresses MAPK Activation and Restores Collagen Deposition in Human Diploid Fibroblasts Challenged with Environmental Levels of UVB

The ultraviolet (UV) component of solar radiation is the driving force of life on earth, but it can cause photoaging and skin cancer. In this study, we investigated the effects of the glucosamine-derivative 2-(N-Acetyl)-L-phenylalanylamido-2-deoxy-β-D-glucose (NAPA) on human primary fibroblasts (FBs) stimulated in vitro with environmental levels of UVB radiation. FBs were irradiated with 0.04 J cm⁻² UVB dose, which resulted a mild dosage as shown by the cell viability and ROS production measurement. This environmental UVB dose induced activation of MAP kinase ERK 1/2, the stimulation of c-fos and at lower extent of c-jun, and in turn AP-1-dependent up-regulation of pro-inflammatory factors IL-6 and IL-8 and suppression of collagen type I expression. On the contrary, 0.04 J cm⁻² UVB dose was not able to stimulate metalloprotease production. NAPA treatment was able to suppress the up-regulation of IL-6 and IL-8 via the inhibition of MAP kinase ERK phosphorylation and the following AP-1 activation, and was able to attenuate the collagen type I down-regulation induced by the UVBs. Taken together, our results show that NAPA, considering its dual action on suppression of inflammation and stimulation of collagen type I production, represents an interesting candidate as a new photoprotective and photorepairing agents.