Potential Risks of Plant Constituents in Dietary Supplements: Qualitative and Quantitative Analysis of Peganum harmala Seeds

The free online trading of herbal mixtures useful for various purposes facilitates the circulation of dangerous herbs or plant parts. This is the case, for example, of the illegal trade in seeds of Peganum harmala (Pgh), which contain alkaloids capable of inhibiting monoamine oxidase (MAO) and are therefore used in hallucinogenic preparations, such as the psychedelic drink ayahuasca. The precise identification of these seeds and their distinction from other very similar but not dangerous seeds are necessary for forensic purposes and represents an advance in avoiding the adulteration of mixtures. In this work, we show the qualitative identification of Pgh seeds by optical and electron microscopy and the parallel development of a real-time qPCR test, which reveals, in a species-specific manner, the presence of Pgh DNA up to quantities lower than 1 pg. In addition to the species specificity and high sensitivity, the reaction accurately quantifies the presence of seeds or parts of seeds of Pgh in complex herbal mixtures, thus giving an indication of the danger or otherwise of the product.     

Antibacterial activity of glutathione-coated silver nanoparticles against Gram positive and Gram negative bacteria

In the present paper, we study the mechanism of antibacterial activity of glutathione (GSH) coated silver nanoparticles (Ag NPs) on model Gram negative and Gram positive bacterial strains. Interference in bacterial cell replication is observed for both cellular strains when exposed to GSH stabilized colloidal silver in solution, and microbicidal activity was studied when GSH coated Ag NPs are (i) dispersed in colloidal suspensions or (ii) grafted on thiol-functionalized glass surfaces. The obtained results confirm that the effect of dispersed GSH capped Ag NPs (GSH Ag NPs) on Escherichia coli is more intense because it can be associated with the penetration of the colloid into the cytoplasm, with the subsequent local interaction of silver with cell components causing damages to the cells. Conversely, for Staphylococcus aureus, since the thick peptidoglycan layer of the cell wall prevents the penetration of the NPs inside the cytoplasm, the antimicrobial effect is limited and seems related to the interaction with the bacterial surfaces. Experiments on GSH Ag NPs grafted on glass allowed us to elucidate more precisely the antibacterial mechanism, showing that the action is reduced because of GSH coating and the limitation of the translational freedom of NPs.     

The toxicity outcome of silica nanoparticles (Ludox?) is influenced by testing techniques and treatment modalities

We analyzed the influence of the kind of cytotoxicity test and its application modality in defining the level of hazard of the in vitro exposures to nanostructures. We assessed the cytotoxicity induced by two different Ludox? silica nanoparticles (NPs), AS30 and SM30, on three human cell lines, CCD-34Lu, A549, and HT-1080. Dynamic light scattering measurements showed particle agglomeration when NPs are diluted in culture medium supplemented with fetal calf serum. We examined the impact of such particle aggregation on the cytotoxicity by exposing the cells to NPs under different treatment modalities: short incubation (2?h) in serum-free medium or long incubation (24–72?h) in serum-containing medium. Under this last modality, NP suspensions tended to form aggregates and were toxic at concentrations five- to tenfold higher than in serum-free medium. The results of cell survival varied considerably when the long-term clonogenic assay was performed to validate the data of the short-term MTS assay. Indeed, the half maximum effective concentrations (EC₅₀) in all the three cell lines were four- to fivefold lower when calculated from the data of clonogenic assay than of MTS. Moreover, the mechanisms of NP toxicity were cell-type-specific, showing that CCD-34Lu are prone to the induction of plasma membrane damages and HT-1080 are prone to DNA double-strand break and apoptosis induction. Taken together, our results demonstrate that the choice of testing strategy and treatment conditions plays an important role in assessing the in vitro toxicity of NPs.

Molecular toolbox for the identification of unknown genetically modified organisms

Competent laboratories monitor genetically modified organisms (GMOs) and products derived thereof in the food and feed chain in the framework of labeling and traceability legislation. In addition, screening is performed to detect the unauthorized presence of GMOs including asynchronously authorized GMOs or GMOs that are not officially registered for commercialization (unknown GMOs). Currently, unauthorized or unknown events are detected by screening blind samples for commonly used transgenic elements, such as p35S or t-nos. If (1) positive detection of such screening elements shows the presence of transgenic material and (2) all known GMOs are tested by event-specific methods but are not detected, then the presence of an unknown GMO is inferred. However, such evidence is indirect because it is based on negative observations and inconclusive because the procedure does not identify the causative event per se. In addition, detection of unknown events is hampered in products that also contain known authorized events. Here, we outline alternative approaches for analytical detection and GMO identification and develop new methods to complement the existing routine screening procedure. We developed a fluorescent anchor-polymerase chain reaction (PCR) method for the identification of the sequences flanking the p35S and t-nos screening elements. Thus, anchor-PCR fingerprinting allows the detection of unique discriminative signals per event. In addition, we established a collection of in silico calculated fingerprints of known events to support interpretation of experimentally generated anchor-PCR GM fingerprints of blind samples. Here, we first describe the molecular characterization of a novel GMO, which expresses recombinant human intrinsic factor in Arabidopsis thaliana. Next, we purposefully treated the novel GMO as a blind sample to simulate how the new methods lead to the molecular identification of a novel unknown event without prior knowledge of its transgene sequence. The results demonstrate that the new methods complement routine screening procedures by providing direct conclusive evidence and may also be useful to resolve masking of unknown events by known events.     

Nano- and femtosecond UV laser pulses to immobilize biomolecules onto surfaces with preferential orientation

By relying on the photonic immobilization technique of antibodies onto surfaces, we realized portable biosensors for light molecules based on the use of quartz crystal microbalances, given the linear dependence of the method on the laser pulse intensity. Here, we compare the quality of the anchoring method when using nanosecond (260 nm, 25 mJ/pulse, 5 ns, 10 Hz rep. rate) and femtosecond (258 nm, 25 μJ/pulse, 150 fs, 10 kHz rep. rate) laser source, delivering the same energy to the sample with the same average power. As a reference, we also tethered untreated antibodies by means of the passive adsorption. The results are striking: When the antibodies are irradiated with the femtosecond pulses, the deposition on the gold plate is much more ordered than in the other two cases. The effects of UV pulses irradiation onto the antibodies are also analyzed by measuring absorption and fluorescence and suggest the occurrence of remarkable degradation when nanosecond pulses are used likely induced by a larger thermal coupling. In view of the high average power required to activate the antibodies for the achievement of the photonic immobilization technique, we conclude that femtosecond rather than nanosecond laser pulses have to be used.     

Asymmetric synthesis of syn and anti methyl 2,3-diamino-3-phenylpropanoate derivatives from N-substituted imines and Schöllkopf's bislactim ether

The reaction between differently N-substituted benzaldimines and (2R)-Schöllkopf's bislactim ether was studied: the azaenolate addition to imines followed by hydrolysis of the resulting adducts gave syn-(2S,3R) and anti-(2S,3S)-methyl 2,3-diamino-3-phenylpropanoate derivatives in good yields. The configurations of the newly formed stereocenters of α,β-diamino acids were assigned on the basis of the ¹H NMR analysis and by comparison with known products. The diastereoisomeric ratios were explained taking into account the effect of the substituent present on the imine nitrogen on the transition state stability. This method represents a new approach for stereoselective synthesis of α,β-diamino acids.     

A Metric Approach to Elastic Reformations

We study a variational framework to compare shapes, modeled as Radon measures on \({\mathbb{R}}^{N}\) , in order to quantify how they differ from isometric copies. To this purpose we discuss some notions of weak deformations termed reformations as well as integral functionals having some kind of isometries as minimizers. The approach pursued is based on the notion of pointwise Lipschitz constant leading to a matric space framework. In particular, to compare general shapes, we study this reformation problem by using the notion of transport plan and Wasserstein distances as in optimal mass transportation theory.     

On the cardinality of n-Urysohn and n-Hausdorff spaces

Two variations of Arhangelskii’s inequality $\left| X \right| \leqslant 2^{\chi (X) - L(X)}$ for Hausdorff X [Arhangel’skii A.V., The power of bicompacta with first axiom of countability, Dokl. Akad. Nauk SSSR, 1969, 187, 967–970 (in Russian)] given in [Stavrova D.N., Separation pseudocharacter and the cardinality of topological spaces, Topology Proc., 2000, 25(Summer), 333–343] are extended to the classes with finite Urysohn number or finite Hausdorff number.     

Tetraaryl ZnII Porphyrinates Substituted at β‐Pyrrolic Positions as Sensitizers in Dye‐Sensitized Solar Cells: A Comparison with meso‐Disubstituted Push–Pull ZnII Porphyrinates

A facile and fast approach, based on microwave‐enhanced Sonogashira coupling, has been employed to obtain in good yields both mono‐ and, for the first time, disubstituted push–pull Zn^II porphyrinates bearing a variety of ethynylphenyl moieties at the β‐pyrrolic position(s). Furthermore, a comparative experimental, electrochemical, and theoretical investigation has been carried out on these β‐mono‐ or disubstituted Zn^II porphyrinates and meso‐disubstituted push–pull Zn^II porphyrinates. We have obtained evidence that, although the HOMO–LUMO energy gap of the meso‐substituted push–pull dyes is lower, so that charge transfer along the push–pull system therein is easier, the β‐mono‐ or disubstituted push–pull porphyrinic dyes show comparable or better efficiencies when acting as sensitizers in DSSCs. This behavior is apparently not attributable to more intense B and Q bands, but rather to more facile charge injection. This is suggested by the DFT electron distribution in a model of a β‐monosubstituted porphyrinic dye interacting with a TiO₂ surface and by the positive effect of the β substitution on the incident photon‐to‐current conversion efficiency (IPCE) spectra, which show a significant intensity over a broad wavelength range (350–650 nm). In contrast, meso‐substitution produces IPCE spectra with two less intense and well‐separated peaks. The positive effect exerted by a cyanoacrylic acid group attached to the ethynylphenyl substituent has been analyzed by a photophysical and theoretical approach. This provided supporting evidence of a contribution from charge‐transfer transitions to both the B and Q bands, thus producing, through conjugation, excited electrons close to the carboxylic anchoring group. Finally, the straightforward and effective synthetic procedures developed, as well as the efficiencies observed by photoelectrochemical measurements, make the described β‐monosubstituted Zn^II porphyrinates extremely promising sensitizers for use in DSSCs.     

High-Energy Ball Milling of NiAl(Fe) System

High-energy ball milling was used to promote the solubilization of iron into NiAl powder for an iron concentration range of 10–30 wt.%. The microstructural evolution induced by the intense mechanical deformations, under different milling conditions, was followed by X-ray diffraction and Mössbauer spectroscopy. The Mössbauer spectra are dominated by a magnetic sextet of about 33 T. Increasing the time and the speed of milling gives rise to a non-resolved doublet, having parameters typical of a NiAl compound with Fe atoms in solution. At the same time a reduction of lattice parameter occurs, which can be correlated to composition variations and partial disordering of the NiAl structure. Subsequent annealing modifies the Mössbauer spectra noticeably. In particular, the non-magnetic component becomes a broad singlet. Both diffraction analysis and Mössbauer spectroscopy indicate that a fcc Ni(Al,Fe) solid solution is forming in samples milled in agate. It is observed that the grain size of the milled products remains in the nanometric range even after thermal treatment, which adds interest to possible applications.