Transfer to the continuum of 14C via (18O, 16O) reaction

A study of the continuum of ¹⁴C populated by the ¹²C(¹⁸O, ¹⁶O)¹⁴C reaction at 84 MeV incident energy has been performed. The ejectiles have been momentum analyzed at forward angles by the MAGNEX magnetic spectrometer. The energy spectra were obtained up to about 20 MeV excitation energy. The scattering of two neutrons independently removed from the projectile as it passes the target nucleus has been described by means of an optical potential with a semi-classical approximation for the relative motion. The calculations describe a significant part of the continuum observed in the energy spectra. In particular, a resonance of the residual nucleus dominates the region near the two-neutron emission threshold.     

Selectivity of the 12C(18O, 16O)14C reaction

A study about the ¹²C(¹⁸O, ¹⁶O)¹⁴C two-neutron transfer reaction was performed at the Catania INFN-LNS laboratory at 84 MeV incident energy. The ¹⁶O ejectiles produced in the reactions were momentum analyzed and identified by the MAGNEX spectrometer. The Q-value spectrum of ¹⁴C shows several known bound and resonant states, in particular states with 2p-4h configuration respect to the ¹⁶O core. The integrated cross sections show an enhanced yield for the two-neutron transfer compared to the one-neutron transfer. These results are some experimental evidences that the (¹⁸O, ¹⁶O) reaction proceeds mainly by the direct transfer of the neutron pair, instead of a second order process.     

MALDI‐TOF mass spectrometry for the monitoring of she‐donkey's milk contamination or adulteration

Donkey's milk (DM), representing a safe and alternative food in both IgE‐mediated and non‐IgE‐mediated cow's milk protein allergy, can be categorized as precious pharma‐food. Moreover, an economically relevant interest for the use of DM in cosmetology is also developing. The detection of adulterations and contaminations of DM is a matter of fundamental importance from both an economic and allergenic standpoint, and, to this aim, fast and efficient analytical approaches to assess the authenticity of this precious nutrient are desirable. Here, a rapid matrix‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry (MALDI‐TOF MS)‐based method aimed to the detection of bovine or caprine milk in raw DM is reported. The presence of the extraneous milks was revealed by monitoring the protein profiles of the most abundant whey proteins, α‐lactalbumin (α‐LA) and β‐lactoglobulin, used as molecular markers. The possibility of obtaining a quantitative analysis of the level of cow or goat milk in DM based on the MALDI‐TOF peak areas of α‐LAs was also explored. The results showed that the experimental quantitative values were in good agreement with the real composition of each mixture. As pretreatment of the milk samples is not required, and owing to the speed and the high sensitivity of MALDI‐MS, the protocol here reported could represent a reliable method for routine analyses aimed to assess the absence of contamination in raw fresh DM samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Sequestering ability of some chelating agents towards methylmercury(II)

A study on the interactions between CH₃Hg⁺ and some S, N and O donor ligands (2-mercaptopropanoic acid (thiolactic acid (H₂ TLA)), 3-mercaptopropanoic acid (H₂ MPA), 2-mercaptosuccinic acid (thiomalic acid (H₃ TMA)), d,l-penicillamine (H₂ PSH), l-cysteine (H₂ CYS), glutathione (H₃ GSH), N,N′-bis(3-aminopropyl)-1-4-diaminobutane (spermine (SPER)), 1,2,3,4,5,6-benzenehexacarboxylic acid (mellitic acid (H₆ MLT)) and ethylenediaminetetraacetic acid (H₄ EDTA)) is reported. The speciation models in aqueous solution and the possible structures of the complexes formed are discussed on the basis of potentiometric, calorimetric, UV spectrophotometric and electrospray mass spectrometric results. For the CH₃Hg⁺–S donor ligand systems, the formation of ML^1–z and MLH^2–z complex species is observed, together with a diprotonated MLH ₂ ^3–z species for CYS ^2?, PSH ^2? and GSH ^3? and the mixed hydrolytic one ML(OH)^?z for TLA ^2? and MPA ^2?. The dependence of the stability on ionic strength and on temperature is also analysed. In the other CH₃Hg⁺-L systems (L?=?MLT ^6?, SPER and EDTA ^4?), ML^1–z , MLH^2–z and MLH₂ ^3–z complex species are formed, together with the MLH₃ ^4–z species for SPER, the mixed hydrolytic ML(OH)^–z one for SPER and EDTA, and the M₂L^2–z for EDTA only. On the basis of the speciation models proposed, the sequestering ability of the ligands towards methylmercury(II) cation is evaluated. All S donor ligands show a good sequestering power (at 10^?11?mol?L^?1 level, in the pH range 4 to 8) following the trend MPA ^2??<?PSH ^2??<?GSH ^3??<?TLA ^2??<?CYS ^2??<?TMA ^3?, while significantly lower is the sequestering ability of MLT, SPER and EDTA (at 10^?3–10^?5?mol?L^?1 level, in the pH range 4 to 8).

Depth distribution of fluorine in enamel teeth by19F(p, α0)16O reaction

Summary Fluorine depth profiles have been measured into enamel of human teeth by using the nuclear reaction¹⁹F(p, α₀)¹⁶O for incoming proton beam at 1350 keV. Details of fluorine distribution over a few micrometres have been obtained by comparison of the energy spectrum of alpha-particles from the reaction in teeth with that of the standard target of CrF₃. The average concentration of fluorine is 1.5 mg/g in the enamel of healthy tooth, while the concentration is below 0.3 mg/g (MDL) in the caried zones. These values can reach 13 mg/g in the enamel of a fluorine tooth.

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Riassunto Usando la reazione nucleare¹⁹F(p, α₀)¹⁶O, con un fascio di protoni incidenti di 1350 keV, sono stati ottenuti i profili di fluoro nello smalto di denti umani sani e fluorotici. Lo studio della distribuzione di fluoro in profondità è stato condotto per confronto degli spettri rivelati dal dente e da campioni standard di CrF₃ di riferimento. La concentrazione media di fluoro riscontrata nello smalto di incisivi sani è stata di 1.5 mg/g. Queste concentrazioni possono raggiungere 13 mg/g nello smalto di incisivi fluorotici. Le zone cariate mostrano una deficienza di fluoro, al di sotto del limite minimo di rivelazione della metodica (MDL=0.3 mg/g).

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Резюме Используя ядерную реакцию¹⁹F(p, α₀)¹⁶O при энергии падающего протонного пучка 1350 кэВ, измеряются распределения фтора по глубине в эмали зубов человека. Характеристики распределения фтора были получены с помощью сравнения энергетического спектра альфа-частиц из реакции в зубе со спектром для стандартной мишени CrF₃. Средняя концентрация фтора составляет 1.5 мг/г в эмали здоровых зубов, тогда как концентрация в кариозных зонах уменьшается до 0.3 мг/г. Эти концентрации могут достигать значений 13 мг/г в эмали фтоти-рованных зубов.

     

Mechanism of thermal degradation of polyurethanes investigated by direct pyrolysis in the mass spectrometer

Direct pyrolysis in the mass spectrometer (MS) yielded unequivocal evidence regarding the mechanism of thermal decomposition of N-monosubstituted and N-disubstituted polyurethanes. It was ascertained that direct pyrolysis in the MS detects the primary thermal fragments that originate from polyurethane pyrolysis. This is particularly useful when, as in the thermal decomposition illustrated in eq. (1), it is necessary to distinguish between primary and secondary thermal fragments in order to assess the thermal degradation mechanism. Our results indicate that N-monosubstituted polyurethane V undergoes a quantitative depolycondensation process. Instead, the thermal decomposition of the N-disubstituted polyurethane VI which occurs selectively in eq. (1) is demonstrated by the detection of thermal fragments that contain secondary amine and olefinic end groups. Finally, polyurethane VI shows a higher thermal stability with respect to polymer V because of the absence of the depolycondensation process, which accounts for the thermal degradation of the N-monosubstituted polyurethane V.     

Detection and sequence determination of a new variant beta-lactoglobulin II from donkey

The sequence determination of a new variant of beta-LG II, detected as a minor component by reversed-phase high-performance liquid chromatography/electrospray ionization mass spectrometry (RP-HPLC/ESI-MS) analysis of the whey fraction from a milk sample taken from an individual donkey belonging to the 'Ragusana' species of eastern Sicily, is reported. Direct RP-HPLC/ESI-MS analysis of the whey fraction from this milk sample allowed the identification of a new variant of beta-LG II, based on the determination of the M(r) of the intact protein. The new protein, with an experimentally determined M(r) of 18311 Da, was detected as a minor component in the whey fraction investigated. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)MS and RP-HPLC/ESI-MS/MS analyses of the tryptic digest of the new protein demonstrate that it presents two amino acid substitutions with respect to the sequence of beta-LG II A, namely a substitution Pro-->Cys at position 110, and a substitution Asp-->Gly at position 162. The disulfide bonds between the four cysteines, not directly determined in donkey's and horse's beta-LG II, were shown to occur between Cys(106)-Cys(120) and Cys(66)-Cys(161), as in other mammalian beta-LGs. The new beta-LG II variant from donkey was named D.     

A multiplex molecular assay for the detection of uniparental disomy for human chromosome 7

Uniparental disomy (UPD) describes the inheritance of both homologues of a pair of chromosomes from only one parent. This condition is often caused by nondisjunction events during meiosis. UPD has been reported as a rare cause of the autosomal recessive disorder and aberrant expression of imprinted genes that are expressed from only one parental allele, either maternal or paternal. Maternal and/or paternal UPD for chromosome 7 is the most frequently observed UPD after UPD15. Here we developed and validated, for the first time, an effective, CE‐based method for a rapid and economic detection based on two‐fluorescent STR multiplexes.