AuSi compound formation induced by ion mixing

Ion bombardment with energetic ions of a thin layer of Au deposited on a silicon substrate gives rise to efficient intermixing. This AuSi intermixed layer has been analyzed with Rutherford back-scattering spectrometry and X-ray photoelectron spectroscopy. The results of these investigations show that AuSi compound formation occurs and that this can provide the driving force for the observed intermixing.     

Identification and characterization of a new beta-casein variant in goat milk by high-performance liquid chromatography with electrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry

A new variant of beta-casein was detected in the casein fraction obtained from milk of a goat belonging to an autochthonous breed of southern Italy, "Argentata dell'Etna". Reversed-phase high-performance liquid chromatography/electrospray ionization mass spectrometry (RP-HPLC/ESI-MS) analysis indicated that the new beta-casein variant, here named D, has a M(r) 15 Da higher than that of variant C previously described. The modification in the amino acid sequence responsible for the 15 Da difference in M(r) between variants C and D was determined by coupling trypsin digestion with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and RP-HPLC/ESI-MS, and it was demonstrated that it is due to the point mutation Val(207) --> Asn(207). The phosphorylation pattern of the new variant D was shown to be identical to that of variant C, as the protein shows two phosphorylation levels, 5 and 6P, occurring with comparable relative abundances. Ser35 was determined as one of the phosphorylation sites, whereas the others were probably analogous to those determined previously for the beta-Cn variant C, at Thr12 and Ser1517-19. The results reported here indicate that the combined use of RP-HPLC/ESI-MS, MALDI-TOFMS and MS/MS represents a powerful tool for the detection and characterization of minor components present in complex protein mixtures.     

Thermal decomposition of flame retardants: Mixtures of chlorinated polymers with Sb2O3 and (BiO)2CO3

The thermal decomposition products that evolve from mixtures of poly(vinyl chloride) (PVC), poly(vinylidene chloride) (PVC₂), and chlorinated paraffin (CP) with Sb₂O₃ and (BiO)₂CO₃, respectively, have been analyzed by a method of direct pyrolysis in the ion source of a mass spectrometer. This method allowed us to detect volatile products with masses as high as 226 (SbCl₃), 314 (BiCl₃), 484 (Sb₄), 580 (Sb₄O₆), and 836 (Bi₄). Except for SbCl₃, this is the first direct evidence of the presence of these species in the gas phase. The volatilization rate profiles of these species versus the pyrolysis temperature have been also determined. Our data confirm that the effectiveness of the title mixtures as flame-retardant agents depends on the transport of volatile metal products in the flame and provide direct evidence of the presence of metallic Sb and Bi below the polymer ignition temperatures.     

The structure of laurobtusol, a new rearranged sesquiterpenoid from the mediterranean red alga laurencia obtusa

An alcohol with a new tricyclic humulane skeleton, laurobtusol was isolated from the Mediterranean Red Alga Laurencia obtusa. The structure was established mainly by 2 D NMR methods and the relative configuration was assigned by a quantitative computer simulation of the lanthanide induced shifts in the ¹H NMR spectrum and Molecular Mechanics calculation (MM2).     

Direct mass spectrometry of polymers. X. Primary thermal fragmentation processes in totally aromatic polyesters

The thermal decomposition of a series of isomeric poly-(oxphthaloyloxyphenylenes) (I–IV) and poly(m-hydroxybenzoic acid) (V) was studied by Direct Pyrolysis–Mass Spectrometry. The results indicate that intramolecular exchange reactions predominate in the primary thermal fragmentation processes, causing the formation of cyclic oligomers which are subsequently cleaved to open-chain fragments. The size and relative abundance of the cycles produced appear to be strongly influenced by steric factors, i.e., by the structure (para or meta) of the repeating unit in each polymer. Remarkably, in the case of poly(m-hydroxybenzoic acid) the formation of cyclic oligomers containing up to seven repeating units is observed.