Microchemical investigations of historical coins

Microchemical investigations were carried out on ancient silver coins originated from the same country but of different historical periods between the fifth and the second centuries B.C. Energy-Dispersive X-ray microanalysis in a Scanning Electron Microscope (SEM-EDX) was employed to obtain qualitative and semi-quantitative information about the chemical composition of these coins. SEM-EDX analyses employ an electron beam of 20?keV, which interacts with the sample leading to the emission of characteristic X-rays, to determine elements present in the surface patina, closely related to the sample preservation. In the X-ray photoelectron spectroscopy (XPS) analysis a monochromatic Al Kα radiation (1486.6?eV) interacts with the sample and photoelectrons are detected as secondary radiation, to investigate about coins elemental composition. Moreover a beam of Ar⁺ ions with an energy of 3?keV was used for the sputtering procedure in order to perform depth profile measurements, from the surface (patina composition) down to deeper layers. Useful information about production, chronological period and utilization places of coins are obtained to support a correct dating of these samples.     

Characterization of polyphenolic compounds in unripe chinotto (Citrus myrtifolia) fruit by HPLC/PDA/ESI/MS-MS

The flavonoid and furocoumarin composition was investigated of peel and pulp tissues of unripe fruits of Citrus myrtifolia Rafinesque, an ingredient of the popular soft drink "chinotto". Compound separation and identification was made using an HPLC-PDA detector coupled to ESI/MS/MS in positive and negative mode. Eighteen compounds (3-hydroxy-3-methylglutaryl-, C- and O-glycosyl flavonoids, furocoumarins and polymethoxylated flavones) were identified and quantified. Data indicated that the overall amount of flavonoids and furocoumarins in peel was higher than in the pulp, even though their relative distribution did not significantly change, apart from a different distribution of flavones and a lower content of naringin in the peel.     

Temperature‐induced self‐assembly of degalactosylated xyloglucan at low concentration

Xyloglucan is a natural polysaccharide having a cellulose‐like backbone and hydroxyl groups‐rich side‐chains. In its native form the polymer is water‐soluble and forms gel only in presence of selected co‐solutes. When a given fraction of galactosyl residues are removed by enzymatic reaction, the polymer acquires the ability to form a gel in aqueous solution at physiological temperatures, a property of great interest for biomedical/pharmaceutical applications. This work presents data on the effect of a temperature increase on degalactosylated xyloglucan dispersed in water at concentration low enough not to run into macroscopic gelation. Results obtained over a wide interval of length scales show that, on increasing temperature, individual polymer chains and pre‐existing clusters self‐assemble into larger structures. The process implies a structural rearrangement over a few nanometers scale and an increase of dynamics homogeneity. The relation of these findings to coil‐globule transition and phase separation is discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1727–1735     

SERS study of a tetrapeptide based on histidine and glycine residues,adsorbed on copper/silver colloidal nanoparticles

Surface‐enhanced Raman scattering has been employed to characterize the adsorption of an oligopeptide containing histidine residues on colloidal nanoparticles of metals as Ag and Cu obtained by laser ablation. The title molecule consists of two histidine and glycine residues alternating along the chain and terminating with an acetyl on one side and an amide group on the other. Histidine residues are found to act as docking sites of the molecule to the surface of the metal nanoparticles. Semiempirical parameterized model number 3 (PM3) calculations performed on molecule/metal model complexes suggest possible different adsorption geometries depending on the metallic substrate. This investigation could provide useful information to address the interaction of protein systems with metal ions, which is often related to fundamental biological process in living systems and can play an important role in different neuropathological diseases. Copyright © 2014 John Wiley & Sons, Ltd.     

Anomalous Fluctuations in the Motion of Partitioning Objects

We study how an object that partitions in two its thermally agitated environment relaxes to its equilibrium fluctuations. Event-driven molecular dynamics indicate that a conventional diffusive-like bound-Brownian motion is reached after a long-lived sub-diffusive regime. The two-stage behavior is not eliminated increasing the number of agitated particles, suggesting that the origin of the effect is a topologically frustrated exploration of phase-space.     

Interaction of bovine serum albumin with chrysotile: spectroscopic and morphological studies

The biodurability of chrysotile fibers, which is related to their cytotoxicity and mutagenic responses, is strongly affected by the surface chemical adsorption of biological molecules. Natural chrysotile is a heterogeneous material in both structure and composition. The availability of synthetic stoichiometric chrysotile of constant structure and uniform morphology has allowed us to investigate its interaction with bovine serum albumin (BSA). By using transmission electron microscopy (TEM) and atomic force microscopy (AFM), we have obtained the first morphological evidence of albumin adsorption onto chrysotile nanocrystals. FTIR spectroscopy was used to quantify modifications of BSA secondary structure that were induced by the surface interaction. The protein transition to beta-turns allows a stronger interaction between the protein hydrophilic side-chains and the charged asbestos surface, which is consistent with hydrogen bonds involving the superficial OH groups. Synthetic stoichiometric chrysotile nanocrystals were shown to be an ideal reference standard with which to study the interaction of asbestos fibers with biological systems, in order to elucidate the chemical mechanisms of asbestos toxicity.     

[4+2]-cycloadditions of thiones with nitrosoalkenes: synthesis of derivatives of 4H-1,5,2-oxathiazine,a new heterocyclic system.

Conjugated nitrosoalkenes, generated $\text{in situ}$$\text{via}$ dehydrobromination of α-bromoketoximes, undergo an easy [4+2]-cycloaddition with thiocarbonyl compounds to give very high yields of the new heterocycles 4H-1,5,2-oxathiazines. The thermolysis and the behaviour to oxidation of these adducts were tested.