Advantages of using a modified orthogonal sampling configuration originally designed for LC-ESI-MS to couple CE and MS for the determination of antioxidant phenolic compounds found in virgin olive oil

A ThermoFinnigan sheath liquid flow capillary electrophoresis-mass spectrometry system designed for coupling via a co-axial interface was coupled through an adapted via an alternative, commercially available interface for orthogonal sampling. The affordable, reversible structural alterations made in the commercial LC-MS interface resulted in improved analytical performance.The results of a conventional capillary electrophoresis (CE) method using a commercial co-axial source to determine antioxidant phenolic acids present in virgin olive oil, were compared with those obtained by using a modified orthogonal sampling position. In both cases, separations were done using a 10 mM ammonium acetate/ammonium hydroxide buffer solution at pH 10.0 and a constant applied voltage of 25 kV. The operating variables for the mass spectrometry interface were re-optimized for the modified orthogonal orientation. This allowed the sheath liquid, sheath gas flow rates and capillary voltage to be lowered with respect to the co-axial coupling configuration. In addition, the orthogonal sampling position provided a higher selectivity by effect of ion sampling excluding larger droplets—with an increased momentum along the axis—which were drained through the sink at the bottom of the ion source. Also, the new configuration facilitated sample ionization, improved electrospray stability and led to stronger signals as a result.The new system was validated in terms of precision (repeatability), linearity, and limits of detection and quantification. A comparison of the validation data with the results previously obtained by using a commercial co-axial configuration revealed the adapted orthogonal sampling position to provide better repeatability in both migration times and relative peak areas (<1% and 7% respectively with n = 15 replicates), a good linear range (with levels in the microgram-per-litre region) and lower limits of detection—especially for the compounds detected with the lowest sensitivity when co-axial ESI was used, as HFA, GEN, FER and VAN finding LOD among 24-3.0 μg L⁻¹ respectively.     

Self-assembled E(2)L(3) cryptands (E = P, As, Sb, Bi): transmetalation, homo- and heterometallic assemblies, and conformational isomerism

A series of Group 15-containing homometallic (E(2)L(3), E = P, As, Sb, Bi) and heterometallic (AsSbL(3), AsBiL(3), PSbL(3)) supramolecular cryptands were prepared by the self-assembly of pnictogen halides with dithiolate ligand or by direct transmetalation from a heavier congener. Structural characterization by single crystal X-ray diffraction shows that the E-S bond distances and S-E-S bond angles are significantly affected by the identity of the pnictogen. (1)H NMR spectroscopy reveals that the homometallic cryptands are dynamic in solution: surprisingly one ligand "flips", perturbing the C(3) symmetry of the complex and giving a new asymmetric conformer. Density functional theory calculations were carried out on both the symmetric and the asymmetric conformations of the cryptands, and the energies were compared to those observed by NMR spectroscopy. It was found that the relative stability of the asymmetric cryptand to its symmetric conformer increases with increasing size of the Group 15 element. Finally, it is reported that if two metals are present during the self-assembly process, heterometallic cryptands form. These supramolecular cryptands are reminiscent of their organic analogues, but result from a self-assembly process rather than a stepwise synthesis. Surprisingly, they possess conformational isomerism and exhibit dynamic transmetalation in their reactivity which provides access to otherwise unattainable assemblies.     

An Improved End-Point Fluorimetric Procedure for the Determination of Low Amounts of Trypsin Activity in Biological Samples Using Rhodamine-110-Based Substrates

A novel end-point fluorimetric procedure based on the use of rhodamine-110-labeled specific substrate was developed to determine trypsin activities in biological samples. We evaluated the ability of trichloroacetic acid and acetic acid to stop the enzymatic reaction without hindering the detection of the fluorescence of rhodamine-110 released into the reaction mixture from the specific substrate (CBZ-l-alanyl-l-arginine)₂-rhodamine-110. Trichloroacetic acid decreased markedly the fluorescence of rhodamine-110, even at low concentrations. On the other hand, the addition of 50 mmol/l acetic acid inactivated efficiently trypsin activity, causing minor effects on rhodamine-110 fluorescence. The proposed procedure was more sensitive than the spectrophotometric end-point method using N-α-benzoyl-dl-arginine-p-nitroanilide as substrate. The possibility of carrying out end-point fluorimetric assays improves the performance of monocell fluorimeters by setting specific conditions optimal for each enzyme activity independently of the fluorimeter. This method also allows replicate assays to be conducted simultaneously, resulting in considerable time saving and in increased performance of low-cost equipment.     

Compact microcubic structures platform based on self-assembly Prussian blue nanoparticles with highly tuneable conductivity

Control of molecular and supramolecular properties is used to obtain a new advanced hybrid material based on Prussian blue nanoparticles (PB NPs). This hybrid material is obtained through a self-assembled Layer-by-Layer (LbL) approach combining the advantageous features of β-cyclodextrin (β-CD) polysaccharides, PB NPs and poly(allylamine hydrochloride) from electrostatic interaction between the deposited layers. Transmission electronic microscopy images suggested that PB NPs were protected by β-CD polysaccharides that prevent the aggregation phenomena. In addition, as confirmed by scanning electronic microscopy images, it was found that PB NPs are organized in microcubic supramolecular like structures via a mesoscale self-assembly process. Interestingly, the 3-bilayer {PAH/PB-CD} film exhibited a higher density of microcubic structures and a high electrochemical response with PB sites available for redox reactions at a supramolecular level. By utilizing fewer bilayers and consequently less material deposition, the formed {PAH/PB-CD} multilayer films of a tuneable conductivity can be expected to have interesting future applications for host-guest like dependent electrochemical biosensing designs.     

Spatial release from masking in normally hearing and hearing-impaired listeners as a function of the temporal overlap of competing talkers

Listeners with sensorineural hearing loss are poorer than listeners with normal hearing at understanding one talker in the presence of another. This deficit is more pronounced when competing talkers are spatially separated, implying a reduced "spatial benefit" in hearing-impaired listeners. This study tested the hypothesis that this deficit is due to increased masking specifically during the simultaneous portions of competing speech signals. Monosyllabic words were compressed to a uniform duration and concatenated to create target and masker sentences with three levels of temporal overlap: 0% (non-overlapping in time), 50% (partially overlapping), or 100% (completely overlapping). Listeners with hearing loss performed particularly poorly in the 100% overlap condition, consistent with the idea that simultaneous speech sounds are most problematic for these listeners. However, spatial release from masking was reduced in all overlap conditions, suggesting that increased masking during periods of temporal overlap is only one factor limiting spatial unmasking in hearing-impaired listeners.     

Behavior of water in contact with model hydrophobic cavities and tunnels and carbon nanotubes

By means of molecular dynamics simulations we analyze the behavior of water in contact with model hydrophobic cavities and tunnels. We study the hydration and filling propensity of cavities and tunnels carved in alkane monolayers and, for comparison, we also study single-walled carbon nanotubes of similar size. Our results will determine the dependence of the filling propensity as a function of cavity size while revealing the dynamical nature of the process with alternation of filled and dry states. Concerning the tunnels built across the monolayer, we shall show that the minimum diameter in order to get filled is about twice as large as that for the carbon nanotubes, thus evidencing a more hydrophobic behavior. The existence of water-water hydrogen bonds, a necessary condition for penetration, will also be made evident.     

On the role of the colloidal stability of mesoporous silica nanoparticles as gene delivery vectors

Mesoporous silica nanoparticles have been synthesized and functionalized with four different types of molecules containing amino groups, i.e., with primary amines only, with quaternary amines, with quaternized cyclic amines, or with polyethylenimine (PEI), which is formed by primary, secondary, and tertiary amines. These nanoparticles were then incubated with reporter plasmids and the ability of the resulting complexes to transfect human cells was studied. Only nanoparticles functionalized with PEI were efficient for transfection. The agglomeration behavior and the electrokinetic potential of the nanoparticle–plasmid complexes have been studied, as well as their cell internalization behavior using a fluorescent-labeled plasmid that allows its monitorization by confocal microscopy. The results indicate that the efficiency of PEI-functionalized nanoparticles for transfection resides to some extent in the different characteristics imparted to the nanoparticles regarding agglomeration and surface charge behavior.     

Bilinear Sobolev–Poincaré Inequalities and Leibniz-Type Rules

The dual purpose of this article is to establish bilinear Poincaré-type estimates associated with an approximation of the identity and to explore the connections between bilinear pseudo-differential operators and bilinear potential-type operators. The common underlying theme in both topics is their applications to Leibniz-type rules in Sobolev and Campanato–Morrey spaces under Sobolev scaling.     

Discretization orders for protein side chains

Proteins are important molecules that are widely studied in biology. Since their three-dimensional conformations can give clues about their function, an optimal methodology for the identification of such conformations has been researched for many years. Experiments of Nuclear Magnetic Resonance (NMR) are able to estimate distances between some pairs of atoms forming the protein, and the problem of identifying the possible conformations satisfying the available distance constraints is known in the scientific literature as the Molecular Distance Geometry Problem (MDGP). When some particular assumptions are satisfied, MDGP instances can be discretized, and solved by employing an ad-hoc algorithm, named the interval Branch & Prune. When dealing with molecules such as proteins, whose chemical structure is known, a priori information can be exploited for generating atomic orderings that allow for the discretization. In previous publications, we presented a handcrafted order for the protein backbones. In this work, we propose 20 new orders for the 20 side chains that can be present in proteins. Computational experiments on artificial and real instances from NMR show the usefulness of the proposed orders.     

Higher-Order Multilinear Poincaré and Sobolev Inequalities in Carnot Groups

The notions of higher-order weighted multilinear Poincaré and Sobolev inequalities in Carnot groups are introduced. As an application, weighted Leibniz-type rules in Campanato-Morrey spaces are established.