MS-based characterization of α(s2) -casein isoforms in donkey's milk

The primary structure of four α(s2) -casein (CN) isoforms, present as minor components in the dephosphorylated CN fraction of a milk sample collected in Eastern Sicily from an individual donkey belonging to the Ragusano breed at middle lactation stage, was determined, using the known donkey's α(s2) -CN (GenBank Acc. No. CAV00691; M(r) 26?028?Da) as reference. Proteins, with experimentally measured M(r) of 25?429, 21?939, 25?203 and 21?713?Da, were isolated by the combined use of reversed-phase high-performance liquid chromatography (RP-HPLC) and two-dimensional polyacrylamide gel electrophoresis. The major spot of each gel, corresponding to a single protein, was digested by trypsin, α-chymotrypsin and endoproteinase Glu-C. The resulting peptide mixtures were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and capillary RP-HPLC/nano-electrospray ionization tandem mass spectrometry, and the data obtained were used for the sequence determination. The isoforms are produced from differential splicing events involving exons 4, 5 and 6 and parts of the exon 17. Copyright ? 2012 John Wiley & Sons, Ltd.     

Fluorine Interactions in a Post‐Metallocene Titanium Catalyst: An ab initio Study

The stability of weak fluorine bonds in homogeneous catalyst is studied at the ab initio level for an arylpyridine post‐metallocene complex. The Ti···F···H_β interaction scheme, involving the agostic bond with titanium and the H‐bond with an H_β in the growing chain, is found to be the the most stable one. A possible optimal overlap involving the fluorine lone pairs is proposed. This three‐center interaction could play a role in the inhibition of H_β transfer to the metal or to the monomer in the termination reactions.

     

The Exfoliation of Graphene in Liquids by Electrochemical,Chemical, and Sonication‐Assisted Techniques: A Nanoscale Study

The different exfoliation routes of graphite to produce graphene by sonication in solvent, chemical oxidation and electrochemical oxidation are compared. The exfoliation process and roughening of a flat graphite substrate is directly visualized at the nanoscale by scanning probe and electron microscopy. The etching damage in graphite and the properties of the exfoliated sheets are compared by Raman spectroscopy and X‐ray diffraction analysis. The results show the trade‐off between exfoliation speed and preservation of graphene quality. A key step to achieve efficient exfoliation is to couple gas production and mechanical exfoliation on a macroscale with non‐covalent exfoliation and preservation of graphene properties on a molecular scale.     

Preparation of Bi2Fe4O9 particles by hydrothermal synthesis and functional properties

In the present study, particles with different Bi₂Fe₄O₉ micro/nanostructures with a few particular morphologies (flower-like nanoplatelets, hierarchical microstructures, perfectly square platelets single crystals, etc.) obtained under specific hydrothermal synthesis conditions were investigated. The role of the processing parameters (such as NaOH concentration, reaction temperature, and reaction duration time) on the phase formation mechanism and on the microstructural characteristics was investigated. All the Bi₂Fe₄O₉ morphologies showed orthorhombic symmetry with space group Pbam. The photocatalytic properties and magnetic behavior as a function of the micro/nanostructural characteristics of various Bi₂Fe₄O₉ powders were determined. In the presence of Bi₂Fe₄O₉, a degradation rate of Rose Bengal in the range of 52–61% was determined after 180?min under UV light irradiation (λ?=?254?nm). Magnetic activity with antiferromagnetic behavior and a transition at ～240?K slightly dependent on the microstructures was found. The role of Bi₂Fe₄O₉ microstructures in the photocatalytic activity and magnetic properties was discussed.     

BaTiO3–ferrite composites with magnetocapacitance and hard/soft magnetic properties

BaTiO₃–ferrite multiphase composites were prepared starting from di-phase mixtures of α-Fe₂O₃ and BaTiO₃ powders. During the sintering step, the formation of small amounts of secondary phases with multifunctional character as BaFe₁₂O₁₉ or Ba₁₂Ti₂₈Fe₁₅O₈₄ was promoted. The resulting multiphase ceramic compounds show interesting dielectric, magnetic and small magnetocapacitance effect at low temperature. The coexistence of different magnetic phases with contrasting coercivities (hard/soft) was detected by the presence of ‘wasp-waisted’ M(H) hysteresis loops and first-order reversal curve analysis. The present approach demonstrates that active materials can be realised by controlling in situ reactions at the interfaces in ferroelectric–magnetic oxide composites.     

Optimal control and long-run dynamics for a spatial economic growth model with physical capital accumulation and pollution diffusion

In this work we analyze the large-time behavior of a spatially structured economic growth model coupling physical capital accumulation and pollution diffusion. This model extends other results in the literature along different directions. Alongside the classical Cobb–Douglas production function, a convex–concave production function is considered. We add a negative feedback to the production function in order to describe the (negative) influence of pollution on output, and therefore on capital accumulation. We also present an optimal control problem for the above model.     

Optimizing Single‐Walled‐Carbon‐Nanotube‐Based Saturable Absorbers for Ultrafast Lasers

The application of single‐walled carbon nanotubes (SWCNTs) as saturable absorbers (SA) in a Nd:glass femtosecond laser is verified as a promising alternative to traditional semiconductor saturable‐absorber mirrors (SESAMs). The shortest laser pulses achieved with a SWCNT‐SA fabricated by the slow‐evaporation method are reported herein. Nearly Fourier‐limited 288 fs pulses are obtained with negative‐dispersion soliton mode‐locking. The importance of the properties of the starting material, such as the degree of purity and the chirality, and the successive slow‐evaporation deposition method is proven by using a multitechnique approach based on X‐ray diffractometry, scanning electron microscopy, and μ‐Raman spectroscopy. The high degree of nanotube alignment on the glass substrate and also the slight metallic character due to electron transfer between the glass matrix and the nanotubes themselves are identified as the main features responsible for the good laser response.     

A second-order perturbation theory route to vibrational averages and transition properties of molecules: general formulation and application to infrared and vibrational circular dichroism spectroscopies

A general formulation to compute anharmonic vibrational averages and transition properties at the second-order of perturbation theory is derived from the Rayleigh-Schro?dinger development. This approach is intended to be applicable to any property expanded as a Taylor series up to the third order with respect to normal coordinates or their associated momenta. The equations are straightforward to implement and can be easily adapted to various properties, as illustrated for the case of electric and magnetic dipole moments. From those, infrared and vibrational circular dichroism spectra can be readily obtained. This fully automatic procedure has been applied to several chiral molecules of small-to-medium sizes and compared to the standard double harmonic approximation and to experimental data.     

CuCl-catalyzed radical cyclisation of N-α-perchloroacyl-ketene-N,S-acetals: a new way to prepare disubstituted maleic anhydrides

The copper-catalyzed radical cyclization (RC) of N-α-perchloroacyl cyclic ketene-N,X(X=O, NR, S)-acetals was studied. While the RC of N-acyl ketene-N,O-acetals was unsuccessful, the 5-endo cyclization of the other ketene acetals provided much better results, with the following order of cyclization efficiency: hexa-atomic cyclic ketene-N,NR-acetals<penta-atomic cyclic ketene-N,S-acetals<hexa-atomic cyclic ketene-N,S-acetals. Invariably the catalytic cycle begins with the formation of a carbamoyl methyl radical. This leads to a cascade of reactions, including a radical polar crossover step, which ends with the formation of the maleimide nucleus, or precursors of this. Products from the RC of the hexa-atomic cyclic ketene-N,S-acetals, were efficiently transformed into disubstituted maleic anhydrides.     

Interfacing multistage mass spectrometry with liquid chromatography or ion mobility separation for synthetic polymer analysis

Synthetic polymers are naturally mixtures of homologs, even in pure form. More complexity is introduced by the presence of different comonomers, end groups and/or macromolecular architectures. The analysis of such systems is substantially facilitated by interfacing mass spectrometry (MS), which disperses based on mass, with an additional level of separation involving either interactive liquid chromatography (LC) or ion mobility (IM) spectrometry, both of which are readily coupled online with electrospray ionization and MS detection. IM-MS separates in the gas phase, post-ionization and, therefore, is ideally suitable for labile and reactive polymers. Its usefulness is illustrated with the characterization of non-covalent siloxane-saccharide complexes, metallosupramolecular assemblies and an air- and moisture-sensitive inorganic polymer, poly(dichlorophosphazene). Conversely, LC-MS which separates in solution phase, before ionization, is most effective for the analysis of polymeric mixtures whose components differ in polarity. Interactive LC conditions can be optimized to disperse by the content of hydrophobic units, as is demonstrated for amphiphilic polyether copolymers and sugar-based nonionic surfactant blends. Both LC-MS and IM-MS can be extended into a third dimension by tandem mass spectrometry (MS(2)) studies on select oligomers, in order to obtain insight into individual end groups and isomeric architectures, comonomer sequences and degree of substitution, for example, by hydrophobic functionalities.