Determination of immunoglobulin G in bovine colostrum and milk by direct biosensor SPR-immunoassay

An automated biosensor surface-plasmon resonance-based assay was developed for the determination of immunoglobulin G (IgG) in bovine milk and colostrum with either goat or rabbit antibovine IgG or protein G used as detecting molecule. The method is configured as a direct and nonlabeled immunoassay, with quantitation against an authentic IgG calibrant. Whole colostrum or milk is prepared for analysis by dilution into buffer. Analysis conditions, including ligand immobilization, flowrate, contact time, and regeneration, were optimized, and nonspecific binding was evaluated. Performance parameters included working range of 15-10 000 ng/mL, method detection limit of 0.08 mg/mL, overall instrument response reproducibility relative standard deviation (RSD(R)) of 0.47%, mean between-run RSD(R) of 10.5% for colostrum, and surface stability over 200 analyses. The proposed method was compared with independent alternative methods. The technique was applied to the measurement of IgG content during early lactation transition from colostrum to milk, as well as in consumer milk, colostrum, and hyperimmune milk powders.     

Influence of the graphite type on the synthesis of polypropylene/graphene nanocomposites

In this work, the synthesis of polypropylene (PP)/graphene nanosheet (GNS) nanocomposites by in situ polymerization using metallocene catalysts was studied. Initial reactions were performed using rac‐Et(Ind)₂ZrCl₂ and rac‐Me₂Si(Ind)₂ZrCl₂ catalysts to select the best one to obtain good molecular weight, thermal properties, and tacticity. Subsequently, PP nanocomposites with different loadings of GNS were obtained. GNS from two different sources [Graphite Nacional (GN) and Graphite Aldrich (GA)] have been used, and the differences between the obtained nanocomposites were evaluated. The GNS and nanocomposites were studied by scanning electronic microcopy, transmission electronic microcopy, and X‐ray diffraction. They showed that the GN nanosheets had lower crystal size and diameter than the GA nanosheets and dispersed better in the PP matrix. Differential scanning calorimetry analyses of both types of nanocomposites showed an increase in the crystallization temperature with increasing graphite loading. The polymeric materials were also characterized by GPC, thermogravimetric analysis, and ¹³C NMR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Complexes of nucleolipid liposomes with single-stranded and double-stranded nucleic acids

We report on the association of anionic liposomes from POP-Ade:POPC (1-palmitoyl-2-oleoyl-phosphatidyladenosine and 1-palmitoyl-2-oleoyl-phosphatidylcholine, respectively) with single- and double-strand nucleic acids, mediated by Ca(2+) bridging. The structural and dynamical features of such complexes are compared with those displayed when the nucleolipid is replaced by POPG (1-palmitoyl-2-oleoyl-sn-phosphatidyl-glycerol), characterized by the same apolar skeleton and negative charge as POP-Ade, but lacking the nucleic polar head. For single-stranded nucleic acids, we demonstrate that specific interactions drive the formation of complexes with nucleolipid liposomes, while no association is present for POPG-based samples. For double-stranded nucleic acids, Ca(2+) bridging promotes association with both liposomal formulations, but the corresponding complexes have different structural features, in terms of size, overall charge and internal liquid-crystalline structure.     

Review about olive oil characterization using high-field nuclear magnetic resonance

In the last years Nuclear Magnetic Resonance (NMR) spectroscopy has found many applications in food analysis. Here, we present a review of the most significant results we have obtained in the olive oil characterization using NMR techniques in combination with multivariate statistical methods.     

Role of the activity coefficient in the dissemination of pH: comparison of primary (Harned cell) and secondary (glass electrode) measurements on phosphate buffer considering activity and concentration scales

Despite recent efforts devoted to assessing both the theoretical rationale and the experimental strategy for assignment of primary pH values, these have not yet been accomplished satisfactorily. Traceability and comparability of pH values are achieved only within the constraints of internationally accepted conventions and predefined conditions that cannot account for all possible situations when pH is measured. Critical parameters to be defined are, in particular, the activity coefficients (γ _i) of the ionic species involved in the equilibrium with the hydrogen ions in the solution, which are usually estimated with the approximation typical of the Debye–Hückel theoretical model. For this paper, primary (Harned cell) measurements (traceable to the SI system) of the pH of a phosphate buffer have been considered and the results have been compared with secondary (glass electrode) measurements obtained by considering either the activity (paH) or concentration (pcH) scale of the hydrogen ions. With conventional approaches based on measurements related to activity or concentration scale, discrepancies emerge which have been assigned to incomplete inferences of γ _i arising from chemical features of the solution. It is shown that fitting and comparable paH and pcH results are attainable if evaluation of γ _i is performed using better estimates of the ionic strength, according to an enhanced application of the Debye–Hückel theory.     

Ab initio pair potentials for the ionic lithium-formate system

The potential energy surfaces for the interatomic interaction in the Li⁺HCOO^– system have been investigated byab initio methods within the rigid-molecule approximation. Analytical potential expressions were fitted to 133 calculated SCF energies for the Li⁺-HCOO^– interaction, 42 SCF energies for the Li⁺-Li⁺ interaction, and 332 SCF energies for the HCOO^–-HCOO^– interaction. The global minimum on the Li⁺-HCOO^– surface is –170 kcal/mol and corresponds to the lithium ion lying on the C₂ axis of the formate ion at 2.2 Å from the carbon atom on the oxygen side. The cation-cation and anion-anion interactions are repulsive everywhere, although the potential surface is markedly anisotropic for the HCOO^–-HCOO^– interaction.     

EPDM accelerated sulfur vulcanization: a kinetic model based on a genetic algorithm

A simple closed form equation for the prediction of crosslinking of EPDM during accelerated sulfur vulcanization is presented. Such a closed form solution is derived from a second order non homogeneous differential equation, deduced from a kinetic model. The kinetic model is based on the assumption that, during vulcanization, a number of partial reactions occurs, both in series and in parallel, which determine the formation of intermediate compounds, including activated and matured polymer. Once written standard first order differential equations for each partial reaction, the differential equation system so obtained is rearranged and, after few considerations, a single second order non homogeneous differential equation with constant coefficients is derived, for which a solution may be found in closed form, provided that the non-homogeneous term is approximated with an exponential function. To estimate numerically the degree of crosslinking, kinetic model constants are evaluated through a simple data fitting, performed on experimental rheometer cure curves. The fitting procedure is a new one, and is achieved using an ad-hoc genetic algorithm, provided that a few points, strictly necessary to estimate model unknown constants with sufficient accuracy, are selected from the whole experimental cure curve. To assess the results obtained with the model proposed, a number of different compounds are analyzed, for which experimental or numerical data are available from the literature. The important cases of moderate and strong reversions are also considered, experiencing a convincing convergence of the analytical model proposed. For the single cases analyzed, partial reaction kinetic constants are also provided.     

Reversible photoswitching of dye-doped core-shell nanoparticles

We present a simple and versatile mechanism for the reversible photoswitching of dye-doped core-shell nanoparticles. Photochromic dithienylethenes are incorporated into the outer shell, close enough to the dyes entrapped in the core to efficiently quench them by energy transfer when photoconverted with UV light. The emission can be switched back on by irradiation with λ > 450 nm.     

Formation of a defect-free π-electron system in single β-phase polyfluorene chains

Single-molecule spectroscopy can help to uncover the underlying heterogeneity of conjugated polymers used in organic electronics, revealing the most effective molecules in an ensemble in terms of the transport of charge and excitation energy. We demonstrate that β-phase polyfluorene chains can form a near-perfect π-electron system, whereas conventional polymers exhibit chromophoric localization due to perturbation of the conjugation. Broad-band excitation spectroscopy demonstrates that only one absorbing and emitting unit is present on the polymer chain with an average length of ～500 repeat units, illustrating that the material effectively behaves as a molecular quantum wire with strong electronic coupling throughout the entire system.