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Humic acids (HAs) content of raw water is an important analytical parameter in water treatment facilities because HAs in the presence of chlorine may lead to the formation of dangerous by-products (e.g., trihalomethanes). The concentration of HAs in water is not directly accessible by common analytical methods due to their heterogeneous chemical structure. The aim of this study was to compare two methods to assess humic acids (HAs) in surface water namely absorbance of ultraviolet light at 254 nm (UV(254)) and total organic carbon (TOC), as well as to evaluate the effects of calcium and magnesium concentrations, pH and sample filtration on the methods' results. An aqueous solution of a commercial HA with 10 mg L(-1) was used in the present work. Quantification of the HA was carried out by both UV(254) and TOC (combustion-infrared method) measurements. UV(254) results were converted to TOC using a calibration curve. The effects of calcium (0-136.3 mg L(-1)) and magnesium (0-34.5 mg L(-1)) concentrations, pH (4.0, 7.0 and 9.0) and sample filtration on UV(254) and TOC measurements of the HA suspension were evaluated. More accurate TOC values of HA suspensions were obtained by the combustion-infrared method than by the UV(254) absorbance method. The higher differences of TOC values between unfiltered and filtered samples were detected in the presence of calcium at pH 9.0 using the spectrophotometric method.

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The present work reports the solvent-free, one-pot functionalization of multiwall carbon nanotubes (CNTs) based on the 1,3-dipolar cycloaddition of azomethine ylides using N-benzyloxycarbonyl glycine and formaldehyde. The surface morphology of the functionalized CNTs was investigated by scanning tunneling microscopy. The effect of temperature on the reaction was studied by thermogravimetry and X-ray photoelectron spectroscopy (XPS). XPS was a key technique for the detailed chemical analysis of the CNT surface. The formation of two major reaction products was observed, namely a cyclic benzyl carbamate and a pyrrolidine. The concentration of the two products varied with reaction temperature and time. At 180 °C, the main product was the cyclic benzyl carbamate, while at 250 °C the major product was the pyrrolidine. This simple, solvent-free chemical procedure yields CNTs with fine-tuned surface functionality.

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Carbon nanotubes (CNTs), functionalized by a cycloaddition reaction, were studied by ultrahigh vacuum scanning tunneling microscopy (STM). The STM images provided evidence for partial or total unzipping of the outer CNT layer. The formation of graphene ribbons was triggered by the STM tip, under specific operating conditions. A model for the unzipping is proposed, based on the perturbation of the pi-conjugation along the CNT surface induced by the cycloaddition reaction.

The reaction of salicylic aldehydes with malononitrile was reinvestigated, and the reaction pathway was followed by 1H NMR spectroscopy. A delicate control of the experimental conditions allowed the synthesis of 2-imino-2H-chromene-3-carbonitriles 1, (2-amino-3-cyano-4H-chromen-4-yl)malononitriles 2, 4-amino-5-imino-2,7-dimethoxy-5H-chromeno[3,4-c]pyridine-1-carbonitrile 12, and (4,5-diamino-1-cyano-1,10b-dihydro-2H-chromeno[3,4-c]pyridin-2-ylidene)malononitrile 13. Two novel 2-iminochromene dimers, with structures 8 and 9, were isolated and fully characterized. The activity of compound 8a on Aspergillus spp. growth and on ochratoxin A production was evaluated. The results of the bioassays indicate that compound 8a, applied at concentrations of 2 mM, totally inhibited the growth of the fungi tested. Ochratoxin A production by Aspergillus alliaceus was reduced by about 93% with a 200 microM solution of this compound. A moderate inhibitory effect was observed for the analogous structure 8b, and no inhibition was registered for compounds 2 and 1, used as synthetic precursors of the dimeric species 8.

Buruli ulcer (BU) is a neglected tropical disease caused by Mycobacterium ulcerans. The tissue damage characteristic of BU lesions is known to be driven by the secretion of the potent lipidic exotoxin mycolactone. However, the molecular action of mycolactone on host cell biology mediating cytopathogenesis is not fully understood. Here we applied two-dimensional electrophoresis (2-DE) to identify the mechanisms of mycolactone's cellular action in the L929 mouse fibroblast proteome. This revealed 20 changed spots corresponding to 18 proteins which were clustered mainly into cytoskeleton-related proteins (Dync1i2, Cfl1, Crmp2, Actg1, Stmn1) and collagen biosynthesis enzymes (Plod1, Plod3, P4ha1). In line with cytoskeleton conformational disarrangements that are observed by immunofluorescence, we found several regulators and constituents of both actin- and tubulin-cytoskeleton affected upon exposure to the toxin, providing a novel molecular basis for the effect of mycolactone. Consistent with these cytoskeleton-related alterations, accumulation of autophagosomes as well as an increased protein ubiquitination were observed in mycolactone-treated cells. In vivo analyses in a BU mouse model revealed mycolactone-dependent structural changes in collagen upon infection with M. ulcerans, associated with the reduction of dermal collagen content, which is in line with our proteomic finding of mycolactone-induced down-regulation of several collagen biosynthesis enzymes. Our results unveil the mechanisms of mycolactone-induced molecular cytopathogenesis on exposed host cells, with the toxin compromising cell structure and homeostasis by inducing cytoskeleton alterations, as well as disrupting tissue structure, by impairing the extracellular matrix biosynthesis.