Antonella Profumo

A Novel Mammalian Flavin-dependent Histone Demethylase

Methylation of Lys residues on histone proteins is a well known and extensively characterized epigenetic mark. The recent discovery of lysine-specific demethylase 1 (LSD1) demonstrated that lysine methylation can be dynamically controlled. Among the histone demethylases so far identified, LSD1 has the unique feature of functioning through a flavin-dependent amine oxidation reaction. Data base analysis reveals that mammalian genomes contain a gene (AOF1, for amine-oxidase flavin-containing domain 1) that is homologous to the LSD1-coding gene. Here, we demonstrate that the protein encoded by AOF1 represents a second mammalian flavin-dependent histone demethylase, named LSD2. The new demethylase is strictly specific for mono- and dimethylated Lys4 of histone H3, recognizes a long stretch of the H3 N-terminal tail, senses the presence of additional epigenetic marks on the histone substrate, and is covalently inhibited by tranylcypromine. As opposed to LSD1, LSD2 does not form a biochemically stable complex with the C-terminal domain of the corepressor protein CoREST. Furthermore, LSD2 contains a CW-type zinc finger motif with potential zinc-binding sites that are not present in LSD1. We conclude that mammalian LSD2 represents a new flavin-dependent H3-Lys4 demethylase that features substrate specificity properties highly similar to those of LSD1 but is very likely to be part of chromatin-remodeling complexes that are distinct from those involving LSD1.

Effects of water-soluble functionalized multi-walled carbon nanotubes examined by different cytotoxicity methods in human astrocyte D384 and lung A549 cells

The widespread projected use of functionalized carbon nanotubes (CNTs) makes it important to understand their potential harmful effects. Two cell culture systems, human A549 pneumocytes and D384 astrocytoma cells, were used to assess cytotoxicity of multi-walled CNTs (MWCNTs) with varying degrees of functionalization. Laboratory-made highly functionalized hf-MW-NH(2) and less functionalized CNTs (MW-COOH and MW-NH(2)) were tested in comparison with pristine MWCNTs, carbon black (CB) and silica (SiO(2)) by MTT assay and calcein/propidium iodide (PI) staining. Purity and physicochemical properties of the test nanomaterials were also determined. In both MTT and calcein/PI assays, highly functionalized CNTs (hf-MW-NH(2)) caused moderate loss of cell viability at doses >or=100 microg/ml being apparently less cytotoxic than SiO(2). In preparations treated with CB or the other nanotube types (pristine MWCNTs, MW-COOH and the less functionalized amino-substituted MW-NH(2)) the calcein/PI test indicated no loss of cell viability, whereas MTT assay apparently showed apparent cytotoxic response, occurring not dose-dependently at exceedingly low CNT concentrations (1 microg/ml). The latter nanomaterials were difficult to disperse showing higher aggregate ranges and tendency to agglomerate in bundle-like form in cell cultures. In contrast, hf-MW-NH(2) were water soluble and easily dispersible in medium; they presented lower aggregate size range as well as considerably lower length to diameter ratios and low tendency to form aggregates compared to the other CNTs tested. The MTT data may reflect a false positive cytotoxicity signal possibly due to non-specific CNT interaction with cell culture components. Thus, these properties obtained by chemical functionalization, such as water solubility, high dispersibility and low agglomeration tendency were relevant factors in modulating cytotoxicity. This study indicates that properties obtained by chemical functionalization, such as water solubility, high dispersibility and low agglomeration tendency are relevant factors in modulating cytotoxicity of CNTs.

Determination of trace elements and evaluation of their enrichment factors in Himalayan lichens.

Within the framework of the Ev-K2-CNR research program of the Italian National Research Council a specific task project has been initiated for the identification of trace elements in lichens in remote high altitude areas. This is to evaluate the possibility of using lichens as biomonitors of trace elements of atmospheric pollution. In this preliminary study, more than 20 elements have been determined in some species of lichens collected at different altitudes (from 1300 to 5000 m) in the region of the Sagarmatha National Park (Nepal). Samples of superficial soils were also collected and analyzed to calculate the trace element enrichment factors (EF) using scandium as a normalizing element. Most of the trace elements were determined by instrumental neutron activation analysis (INAA), while lead and cadmium measurements were carried out with electrothermal atomic absorption spectroscopy (ET-AAS). The EF values as well as the elemental concentrations are reported and discussed.

Photochemical degradation of marbofloxacin and enrofloxacin in natural waters.

The photochemical fate of Marbofloxacin (MAR) and Enrofloxacin (ENR), two Fluoroquinolones (FQs) largely used as veterinary bactericides known to be present in surface waters, was investigated in aqueous solution. The degradation of these pollutants (5-50 microg L(-1) starting concentration) was complete in about 1 h by exposure to solar light (summer) and obeyed a first-order kinetics. The structure of the primary photoproducts was determined. Those from ENR arose through three paths, namely, oxidative degradation of the piperazine side-chain, reductive defluorination, and fluorine solvolysis. More heavily degraded products that had been previously reported were rationalized as secondary photoproducts from the present ones. As for MAR, this underwent homolytic cleavage of the tetrahydrooxadiazine moiety to give two quinolinols. All of the primary products were themselves degraded in about 1 h. The photoreactions rates were scarcely affected by Ca(2+) (200 mg L(-1)), Mg(2+) (30 mg L(-1)), Cl(-) (30 mg L(-1)), and humic acid (1 mg L(-1)), but increased in the presence of phosphate (20 mg L(-1)). The fastest degradation of ENR occurred at pH about 8 where the zwitterionic form was present, while in the case of MAR the cationic form was the most reactive.

STRUCTURE AND MEDIUM-DEPENDENT PHOTODECOMPOSITION OF FLUOROQUINOLONE ANTIBIOTICS

The photochemical reactivity of four fluoroquinolone antibiotics is examined. For norfloxacin (NOR), enoxacin (ENX) and lomefloxacin (LOM), the only process occurring is defluorination (from position 6 for the first two drugs, from position 8 for the last one). The quantum efficiency is both structure and medium dependent (4 close to 0.5 both in water and in 0.1 M phosphate buffer for LOM,‐ 0.01 for ENX and 0.004 for NOR in buffer, but more than an order of magnitude higher in neat water). Ofloxacin (OFL) is less light sensitive φ 0.001) and undergoes, in part, reactions different from defluorination. The photoreaction involves heterolytic C‐F bond fragmentation and its efficiency is determined by the internal charge‐transfer character of the excited state (increasing in the series OFL < NOR < ENX < LOM according to the electronegativity of the substituent in position 8) and by the stabilization of the resulting aryl cation (larger for the 8‐cation than for the 6‐cation). The relevance of these data for the rationalization of the known phototoxicity of these drugs is discussed.

Separation of alkanes and aromatic compounds by packed column gas chromatography using functionalized multi-walled carbon nanotubes as stationary phases.

In the present work, we show a novel application of pristine and functionalized Multi-Walled Carbon Nanotubes (MWCNTs) as stationary phase in low-cost packed columns for the gas chromatographic separation of alkanes and aromatic hydrocarbons. The MWCNTs were deeply investigated by means of physical and chemical methods, like thermal analysis, IR and atomic force microscopy, and Inverse Gas Chromatography (IGC) in order to correlate the adsorption process and surface properties with the material purity level and functionalization degree. The derivatization process of the pristine nanotubes was a key factor to achieve a successful separation of both the light n-alkanes (C3-C5) and the related isomers (C4-C5 branched alkanes). Satisfactory results were similarly obtained in the case of separation of aromatic hydrocarbons (BTX).

Fluoroquinolone antibiotics in environmental waters: sample preparation and determination.

The aim of this review is to provide a general overview on the analytical methods proposed in the last decade for trace fluoroquinolone (FQ) determination in environmental waters. A large number of studies have been developed on this topic in reason of the importance of their monitoring in the studies of environmental mobility and potential degradation pathways. Every step of the analysis has been carefully considered, with a particular attention to sample preparation, in relationship with the problems involved in the analysis of real matrices. The different strategies to minimise interference from organic matter and to achieve optimal sensitivity, especially important in those samples with lower FQ concentrations, were also highlighted. Results and progress in this field have been described and critically commented. Moreover, a worldwide overview on the presence of FQs in the environmental waters has been reported.

Analytical application of carbon nanotubes, fullerenes and nanodiamonds in nanomaterials-based chromatographic stationary phases: A review

An overview of the most significative results so far attained in the application of carbon nanotubes, fullerenes and nanodiamonds as chromatographic separation media is presented. In particular, the authors focus on their use in capillary and packed-column gas chromatography, in high performance liquid chromatography and capillary electrochromatography, paying also attention to recently developed stationary phases for fast chromatography and nanochromatography. The performance of the nanomaterials is compared to that of planar and amorphous carbon sorbents and critically discussed in regard to retentive capability and selectivity. A wide part of this review is devoted to the most recent improvements achieved in terms of selectivity by use of functionalized nanotubes and by combination of carbon nanotubes with ionic liquids. Practical aspects of synthetic procedures in preparing novel stationary phases in relationship with their chromatographic behaviour are also commented.

Improving selectivity in gas chromatography by using chemically modified multi-walled carbon nanotubes as stationary phase.

Amino-terminated alkyl MWCNTs (MWCNTs-R-NH2), synthesized by chemical modification of the nanotube skeleton by nucleophilic substitution with 2,2′-(ethylenedioxy)diethylamine, were successfully used as stationary phases for gas chromatographic separation of esters and chloroaromatics. The presence of alkyl chains with polar embedded groups made the functionalized MWCNTs (f-MWCNTs) a mixed-mode GC separation material able to interact in different ways with the analytes. Compared with non-functionalized MWCNTs (nf-MWCNTs), MWCNTs-R-NH2 had higher selectivity, enhanced resolution, and optimum retention behaviour, and they were proved to perform better than the commercial stationary phase Porapak QS (PQS), claimed to be suitable for similar applications. The so-prepared stationary phase was used for analysis of a synthetic mixture containing different classes of analytes, viz. esters, ketones, alcohols, alkanes, and aromatic hydrocarbons, and finally used for investigation of similar real matrices. In particular, the constituents of a commercial paint thinner were determined by direct injection of the sample, with good reproducibility (inter-day precision RSDs from 5 to 19%). Two unknown samples of commercial white spirit were also analysed for determination of the aromatic hydrocarbon content, and their composition was profiled on the basis of the different compounds identified.

Sunlight-induced degradation of soil-adsorbed veterinary antimicrobials Marbofloxacin and Enrofloxacin

Marbofloxacin (MAR) and Enrofloxacin (ENR), two largely employed veterinary Fluoroquinolones (FQs), were found to be present at the micrograms per kilogram level in agricultural soils of South Lombardy (Italy) several months after manuring. Distribution coefficients (K(d)) from sorption experiments indicated a strong binding to the soil. Soil samples fortified with environmentally significant FQs amounts (0.5 mg kg(-1)) were exposed to solar light that promoted extensive degradation (80%) of both drugs in 60-150 h. Thus, photochemistry could be considered a significant depollution path in the soil, although it was two orders of magnitudes slower than in aqueous solution and a fraction of the drug (ca. 20%) remained unaffected. For MAR the photoprocess was the same as in solution, and involved cleavage of the tetrahydrooxadiazine ring. On the contrary, with ENR only some of the photoproducts determined in water (those arising from a stepwise oxidation of the piperazine side chain) were observed. Substitution of the 6-fluoro by a hydroxyl group and reduction did not occur in the soil, supporting the previous contention that such processes required polar solvation of FQs. Consistently with this rationalization, the irradiation of thin layers of solid drugs led to essentially the same products distribution as in the soil. From the environmental point of view it is important to notice that photodegradation mainly affects the side-chains, while the fluoroquinolone ring, to which the biological effect is associated, is conserved up to the later stages of the degradation.