Least-squares support vector machines and near infrared spectroscopy for quantification of common adulterants in powdered milk

This paper proposes the use of the least-squares support vector machine (LS-SVM) as an alternative multivariate calibration method for the simultaneous quantification of some common adulterants (starch, whey or sucrose) found in powdered milk samples, using near-infrared spectroscopy with direct measurements by diffuse reflectance. Due to the spectral differences of the three adulterants a nonlinear behavior is present when all groups of adulterants are in the same data set, making the use of linear methods such as partial least squares regression (PLSR) difficult. Excellent models were built using LS-SVM, with low prediction errors and superior performance in relation to PLSR. These results show it possible to built robust models to quantify some common adulterants in powdered milk using near-infrared spectroscopy and LS-SVM as a nonlinear multivariate calibration procedure.     

Mild and efficient iodination of aromatic and heterocyclic compounds with the NaClO2/NaI/HCl system

NaClO₂/NaI in the presence of HCl is a mild, cheap, and non-toxic reagent for the iodination of phenols, including estradiol and naphthol, aromatic amines, and heterocyclic substrates, e.g., indoles, 8-hydroxyquinoline, imidazole, in fair to excellent yields by a very simple isolation protocol. The scope of the procedure is exemplified by the first iodination of 5-nitroindole to 3-iodo-5-nitroindole in 75% yield.     

Geometric Hermite interpolation by spatial Pythagorean-hodograph cubics

It is shown that, depending upon the orientation of the end tangents t₀,t₁ relative to the end point displacement vector p=p₁–p₀, the problem of G¹ Hermite interpolation by PH cubic segments may admit zero, one, or two distinct solutions. For cases where two interpolants exist, the bending energy may be used to select among them. In cases where no solution exists, we determine the minimal adjustment of one end tangent that permits a spatial PH cubic Hermite interpolant. The problem of assigning tangents to a sequence of points p₀,...,p_n in R³, compatible with a G¹ piecewise-PH-cubic spline interpolating those points, is also briefly addressed. The performance of these methods, in terms of overall smoothness and shape-preservation properties of the resulting curves, is illustrated by a selection of computed examples.     

Effect of Tomato Peel Extract Grown under Drought Stress Condition in a Sarcopenia Model

Tomatoes and their derivates represent an important source of natural biologically active components. The present study aims to investigate the protective effect of tomato peel extracts, grown in normal (RED-Ctr) or in drought stress (RED-Ds) conditions, on an experimental model of sarcopenia. The phenolic profile and total polyphenols content (TPC) of RED-Ctr and RED-Ds were determined by Ultra High-Performance Liquid Chromatography (UHPLC) analyses coupled to electrospray ionization high-resolution mass spectrometry (ESI-HR-MS). Human skeletal muscle myoblasts (HSMM) were differentiated in myotubes, and sarcopenia was induced by dexamethasone (DEXA) treatment. Differentiation and sarcopenia were evaluated by both real-time PCR and immunofluorescent techniques. Data show that myosin heavy chain 2 (MYH2), troponin T (TNNT1), and miogenin (MYOG) were expressed in differentiated myotubes. 5 μg Gallic Acid Equivalent (GAE/mL) of TPC from RED-Ds extract significantly reduced muscle atrophy induced by DEXA. Moreover, Forkhead BoxO1 (FOXO1) expression, involved in cell atrophy, was significantly decreased by RED-Ds extract. The protective effect of tomato peel extracts depended on their qualitative polyphenolic composition, resulting effectively in the in vitro model of sarcopenia.     

Highly Efficient Trityl-Nitroxide Biradicals for Biomolecular High-Field Dynamic Nuclear Polarization

Dynamic nuclear polarization (DNP) is a powerful method to enhance the sensitivity of solid-state magnetic nuclear resonance (ssNMR) spectroscopy. However, its biomolecular applications at high magnetic fields (preferably>14 T) have so far been limited by the intrinsically low efficiency of polarizing agents and sample preparation aspects. Herein, we report a new class of trityl-nitroxide biradicals, dubbed SNAPols that combine high DNP efficiency with greatly enhanced hydrophilicity. SNAPol-1, the best compound in the series, shows DNP enhancement factors at 18.8 T of more than 100 in small molecules and globular proteins and also exhibits strong DNP enhancements in membrane proteins and cellular preparations. By integrating optimal sensitivity and high resolution, we expect widespread applications of this new polarizing agent in high-field DNP/ssNMR spectroscopy, especially for complex biomolecules.     

Effect of chitosan and thiolated chitosan coating on the inhibition behaviour of PIBCA nanoparticles against intestinal metallopeptidases

Surface modified nanoparticles composed of poly(isobutylcyanoacrylate) (PIBCA) cores surrounded by a chitosan and thiolated chitosan gel layer were prepared and characterized in previous works. The presence of such biopolymers on the nanoparticle surface conferred those nanosystems interesting characteristics that might partially overcome the gastrointestinal enzymatic barrier, improving the oral administration of pharmacologically active peptides. In the present work, the antiprotease behaviour of this family of core–shell nanoparticles was in vitro tested against two model metallopeptidases present in the gastrointestinal tract (GIT): Carboxypeptidase A -CP A- (luminal protease) and Leucine Aminopeptidase M -LAP M- (membrane protease). As previous step, the zinc-binding capacity of these nanoparticles was evaluated. Interestingly, an improvement of both the zinc-binding capacity and the antiprotease effect of chitosan was observed when the biopolymers (chitosan and thiolated chitosan) were used as coating component of the core–shell nanoparticles, in comparison with their behaviour in solution, thanks to the different biopolymer chains rearrangement. The presence of amino, hydroxyl and thiol groups on the nanoparticle surface promoted zinc binding and hence the inhibition of the metallopeptidases analysed. On the contrary, the occurrence of a cross-linked structure in the gel layer surrounding the PIBCA cores of thiolated formulations, due to the formation of interchain and intrachain disulphide bonds, partially limited the inhibition of the proteases. The low accessibility of cations to the active groups of the cross-linked polymeric shell was postulated as a possible explanation of this behaviour. Results obtained in this work make this family of surface-modified nanocarriers promising candidates for the successfull administration of pharmacologically active peptides and proteins by the oral route.     

Comments on selected fundamental aspects of microarray analysis

Microarrays are becoming a ubiquitous tool of research in life sciences. However, the working principles of microarray-based methodologies are often misunderstood or apparently ignored by the researchers who actually perform and interpret experiments. This in turn seems to lead to a common over-expectation regarding the explanatory and/or knowledge-generating power of microarray analyses. In this note we intend to explain basic principles of five (5) major groups of analytical techniques used in studies of microarray data and their interpretation: the principal component analysis (PCA), the independent component analysis (ICA), the t-test, the analysis of variance (ANOVA), and self organizing maps (SOM). We discuss answers to selected practical questions related to the analysis of microarray data. We also take a closer look at the experimental setup and the rules, which have to be observed in order to exploit microarrays efficiently. Finally, we discuss in detail the scope and limitations of microarray-based methods. We emphasize the fact that no amount of statistical analysis can compensate for (or replace) a well thought through experimental setup. We conclude that microarrays are indeed useful tools in life sciences but by no means should they be expected to generate complete answers to complex biological questions. We argue that even well posed questions, formulated within a microarray-specific terminology, cannot be completely answered with the use of microarray analyses alone.     

Atomic control of water interaction with biocompatible surfaces: the case of SiC(001)

The interaction of water with Si- and C- terminated beta-SiC(001) surfaces was investigated by means of ab initio molecular dynamics simulations. Irrespective of coverage, varied from 1/4 to 1 monolayer, we found that water dissociates on the Si-terminated surface, substantially modifying the clean surface reconstruction, while the C-terminated surface is nonreactive and hydrophobic. Based on our results, we propose that STM images and photoemission experiments may detect specific changes induced by water on both the structural and electronic properties of SiC(001) surfaces.     

Methane activation by silica-supported Zr(IV) hydrides: the dihydride [(triple bond)SiO)2ZrH2] is much faster than the monohydride [(triple bond)SiO)3ZrH

The silica-supported Zr(iv) dihydride [(triple bond)SiO)2ZrH2] reacts quickly and completely with methane to yield [(triple bond)SiO)2ZrMe2] through the intermediate [(triple bond)SiO)2ZrHMe], while its monohydride analogue [(triple bond)SiO)3ZrH] yields the monomethylated product [(triple bond)SiO)3ZrMe] slowly and incompletely.