Identification, Quantitation, and Sensory Evaluation of Thiols in Bordeaux Red Wine with Characteristic Aging Bouquet.

Great Bordeaux red wines are known for their distinctive aging bouquet. However, the nature of volatile chemicals underpinning this sensory expression is not fully understood. This work investigated the empyreumatic aging bouquet of a collection of premium Bordeaux red wines using silver-ion (Ag+) solid-phase extraction, cryogenic heart-cutting multidimensional gas chromatography mass spectrometry/olfactometry, and comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry. In doing so, a substantial number of "meaty" odors were revealed. Three detected "meaty" notes were tentatively or unequivocally attributed to furan thiols. Among them, 2-methyltetrahydrofuran-3-thiol (1) with a pleasant "meaty" aroma was reported in wine for the first time. Its trans isomer (trans-1a) was resolved from its racemate by chemical modification, which confirmed its presence in wine. The odor detection threshold of trans-1a in the model wine was determined at 55 ng/L. Moreover, an additive effect between 1 and literature-known 2-methyl-3-furanthiol was observed. By a new ultra high-performance liquid chromatography quadrupole Orbitrap high-resolution mass spectrometry method, the concentration of trans-1a, in addition to those of 2-methyl-3-furanthiol and 2-furfuryl thiol, was measured in the wines at ng/L levels.

Asymmetric Allenylation of Alkynes mediated by Chiral Organoselenated Reagents under Oxidative Conditions.

The reactivity of novel chiral lactamide-substituted diselenide-based reagents under oxidative conditions was exploited to develop a metal-free method for the preparation of enantioenriched allenylamides from simple alkynes in good yields, and with enantiomeric excesses up to 99 %. The key of the success in this method is attributed to the hydrogen-bonded lactamide appendages that ensure configurational stability of chiral vinyl selenoxide intermediates for an optimal enantiotopic ß-syn-elimination step.

Induced circular dichroism from helicoidal nano substrates to porphyrins: the role of chiral self-assembly.

Because the combination of chiral and magnetic properties is becoming more and more attractive for magneto-chiral phenomena, we here aim at exploring the induction of chirality to achiral magnetic molecules as a strategy for the preparation of magneto-chiral objects. To this end, we have associated free base- and metallo-porphyrins with silica nano helices, using a variety of elaboration methods, and have studied them mainly by electronic natural circular dichroism (NCD) and magnetic circular dichroism (MCD) spectroscopies. While electrostatic or covalent surface grafting uniformly yielded very low induced CD (ICD) for the four assayed porphyrins, a moderate response was observed when the porphyrins were incorporated into the interior of the double-walled helices, likely due to the association of the molecules with the chirally-organized gemini surfactant. A generally stronger, but more variable, ICD was observed when the molecules were drop casted onto the helices immobilised on a quartz plate, likely due to the different capacities of the porphyrins to aggregate into chiral assemblies. Electronic spectroscopy, electron microscopy and IR spectroscopy were used to interpret the patterns of aggregation and their influence on ICD and MCD. No enhancement of MCD was observed as a result of association with the nanohelices except in the case of the free base, 5,10,15,20-tetra-(4-sulfonatophenyl)porphyrin (TPPS). This nanocomposite demonstrated a large ICD in the Soret region and a large MCD in the Q-region due to J-aggregation. However, no induced MChD was observed, possibly due to the spectral mismatch between the ICD and MCD peaks.

Sequential chiral induction between organic and inorganic supramolecular helical assemblies for the in situ formation of chiral carbon dots.

Self-organised helical bilayers of dicationic gemini surfactants confined in helical silica nanospace were transformed in situ to carbon dots (CDots) via pyrolysis. These water-dispersible CDots exhibit electronic absorption spanning the UV and visible range and possess symmetrical circular dichroism (CD) signals, the sign of which depends on the handedness of the helices.

Use of Conglomerate Mixed Crystals to Deracemize a Stable Racemic-Compound-Forming System.

Deracemization extended to racemic-compound-forming systems is demonstrated. We present here the first results of an alternative for the resolution of systems that exhibit a stable racemic compound but also a closely related conglomerate-forming system. If the couples of enantiomers forming the racemic compound and the enantiomers of the stable conglomerate can syncrystallize in mirror-related partial solid solutions, it is possible to deracemize the racemic mixture of mixed crystals to access to a single handedness. The evidence for this possibility is given in three examples by using temperature-cycling-induced deracemization.

Probing proton diffusion as a guide to environmental stability in powder-engineered FAPbI3 and CsFAPbI3 perovskites.

Formamidinium lead iodide-based solar cells show promising device reliability. The grain imperfection can be further suppressed by developing powder methodology. The water uptake capability is critical for the stability of α-formamidinium lead triiodide (FAPbI3) thin films, and elucidating the migration of hydrogen species is challenging using routine techniques such as imaging or mass spectroscopy. Here, we decipher the proton diffusion to quantify indirect monitoring of H migration by following the N-D vibration using transmission infrared spectroscopy. The technique allows a direct assessment of the perovskite degradation associated with moisture. The inclusion of Cs in FAPbI3, reveals significant differences in proton diffusion rates, attesting to its impact. CsFAPbI3's ability to block the active layer access by water molecules is five times higher than α-FAPbI3, which is significantly higher than methylammonium lead triiodide (MAPbI3). Our protocol directly probes the local environment of the material to identify its intrinsic degradation mechanisms and stability, a key requirement for optoelectronic applications.

Synthesis and Chiroptical Properties of a Chiral Isotopologue of syn-Cryptophane-B.

We report the synthesis and absolute configuration (AC) of a chiral isotopologue of syn-cryptophane-B. Low chiral signatures were measured by polarimetry and electronic circular dichroism, whereas most significant chiroptical effects were observed by vibrational circular dichroism (VCD) and Raman optical activity (ROA). The comparison of experimental VCD and ROA spectra with those predicted by DFT calculations allows the determination of the AC of the two enantiomers as (-)589-MP-syn-2 and (+)589-PM-syn-2.

Chiral analysis of E-ε-viniferin enantiomers, towards a new chemotaxonomic marker of the vine.

BACKGROUND: The accurate characterization of grapevine cultivars (Vitis vinifera) is crucial for grape growers, winemakers, wine sellers, consumers and authorities, considering that mistakes could involve significant damage to the wine economic system. To avoid any misunderstanding, morphological, molecular and chemical tools are developed to positively identify grape varieties. RESULTS: E-ε-viniferin is a stilbene dimer mainly present in the woody part of grapevine and present as a mixture of two enantiomers: (7aR, 8aR)-(-)-E-ε-viniferin (1) and (7aS, 8aS)-(+)-E-ε-viniferin (2). In addition to phenotypic and genotypic approaches, a chemotaxonomic method using E-ε-viniferin enantiomers as chemical markers of grapevine cultivars was investigated. The isolation and purification of E-ε-viniferin enantiomers by preparative high-performance liquid chromatography (HPLC) and chiral HPLC from 14 red and eight white grapevine cane cultivars enabled us to determine the proportion of each enantiomer and therefore to calculate the enantiomeric excess for each variety. The relative abundance of each E-ε-viniferin enantiomer permitted us to distinguish grape varieties, as well as to establish cultivar relationships and patterns through statistical analysis. CONCLUSION: This pioneering work highlighting the enantiomeric excess of E-ε-viniferin as a chemical marker of grapevine paves the way for further studies to understand what mechanisms are involved in the production of these enantiomers in grapevine. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Cooperative interaction between organic and inorganic moieties in hybrid silica nanohelices for enantioselective interaction.

Hybrid nanometric helical structures formed by the molecular assemblies of dicationic gemini surfactants with tartrate counterions covered with helical silica walls interact differently with matching or mismatching enantiomers of the tartrate. The difference of the interaction is based on the cooperativity between the chiral crystalline gemini surfactant molecular organization/conformation and the rigid chiral nanospace formed by the helical silica wall.

Chiroptical and potential in vitro anti-inflammatory properties of viniferin stereoisomers from grapevine (Vitis vinifera L.).

Determination of stereochemistry and enantiomeric excess in chiral natural molecules is a research of great interest because enantiomers can exhibit different biological activities. Viniferin stilbene dimers are natural molecules present in grape berries and wine but also, in larger amount, in stalks of grapevine. Four stereoisomers of viniferin stilbene dimers (7aS,8aS)-E-ε-viniferin (1a), (7aR,8aR)-E-ε-viniferin (1b), (7aS,8aR)-E-ω-viniferin (2a), and (7aR,8aS)-E-ω-viniferin (2b) were isolated from grapevine stalks of Cabernet Sauvignon, Merlot and Sauvignon Blanc, using a combination of centrifugal partition chromatography (CPC), preparative and chiral HPLC. The structure elucidation of these molecules was achieved by NMR whereas the absolute configurations of the four stereoisomers were investigated by vibrational circular dichroism spectroscopy in combination with density functional theory (DFT) calculations. This study unambiguously established the (+)-(7aS,8aS) and (+)-(7aR,8aS) configurations for E-ε-viniferin and E-ω-viniferin, respectively. Finally, we show that Cabernet Sauvignon provided the quasi enantiopure (+)-(7aS,8aS)-E-ε-viniferin compound which presents the best anti-inflammatory and anti-oxidant activities.

Silane-Based SAMs Deposited by Spin Coating as a Versatile Alternative Process to Solution Immersion.

Functionalization of silica surfaces with silane-based self-assembled monolayers (SAMs) is widely used in material sciences to tune surface properties and introduce terminal functional groups enabling subsequent chemical surface reactions and immobilization of (bio)molecules. Here, we report on the synthesis of four organotrimethoxysilanes with various molecular structures and we compare their grafting by spin coating with the one performed by the conventional solution immersion method. Strikingly, this study clearly demonstrates that the spin coating technique is a versatile, fast, and more convenient alternative process to prepare robust, smooth, and homogeneous SAMs with similar properties and quality as those deposited via immersion. SAMs were characterized by PM-IRRAS, AFM, and wettability measurements. SAMs can undergo several chemical surface modifications, and the reactivity of amine-terminated SAM was confirmed by PM-IRRAS and fluorescence measurements.

Neurons with Cat's Eyes: A Synthetic Strain of α-Synuclein Fibrils Seeding Neuronal Intranuclear Inclusions.

The distinct neuropathological features of the different α-Synucleinopathies, as well as the diversity of the α-Synuclein (α-Syn) intracellular inclusion bodies observed in post mortem brain sections, are thought to reflect the strain diversity characterizing invasive α-Syn amyloids. However, this "one strain, one disease" view is still hypothetical, and to date, a possible disease-specific contribution of non-amyloid factors has not been ruled out. In Multiple System Atrophy (MSA), the buildup of α-Syn inclusions in oligodendrocytes seems to result from the terminal storage of α-Syn amyloid aggregates first pre-assembled in neurons. This assembly occurs at the level of neuronal cytoplasmic inclusions, and even earlier, within neuronal intranuclear inclusions (NIIs). Intriguingly, α-Syn NIIs are never observed in α-Synucleinopathies other than MSA, suggesting that these inclusions originate (i) from the unique molecular properties of the α-Syn fibril strains encountered in this disease, or alternatively, (ii) from other factors specifically dysregulated in MSA and driving the intranuclear fibrillization of α-Syn. We report the isolation and structural characterization of a synthetic human α-Syn fibril strain uniquely capable of seeding α-Syn fibrillization inside the nuclear compartment. In primary mouse cortical neurons, this strain provokes the buildup of NIIs with a remarkable morphology reminiscent of cat's eye marbles (see video abstract). These α-Syn inclusions form giant patterns made of one, two, or three lentiform beams that span the whole intranuclear volume, pushing apart the chromatin. The input fibrils are no longer detectable inside the NIIs, where they become dominated by the aggregation of endogenous α-Syn. In addition to its phosphorylation at S129, α-Syn forming the NIIs acquires an epitope antibody reactivity profile that indicates its organization into fibrils, and is associated with the classical markers of α-Syn pathology p62 and ubiquitin. NIIs are also observed in vivo after intracerebral injection of the fibril strain in mice. Our data thus show that the ability to seed NIIs is a strain property that is integrally encoded in the fibril supramolecular architecture. Upstream alterations of cellular mechanisms are not required. In contrast to the lentiform TDP-43 NIIs, which are observed in certain frontotemporal dementias and which are conditional upon GRN or VCP mutations, our data support the hypothesis that the presence of α-Syn NIIs in MSA is instead purely amyloid-strain-dependent.

Improving Orientation, Packing Density, and Molecular Arrangement in Self-Assembled Monolayers of Bianchoring Ferrocene-Triazole Derivatives by "Click" Chemistry.

This work describes the self-assembled monolayers (SAMs) of two ferrocene derivatives with two anchoring groups (at the bottom and at the top of the SAM) deposited on ultraflat template-stripped gold substrates by cyclic voltammetry and analyzed by complementary surface characterization techniques. The SAM of each molecule is deposited by three different protocols: direct deposition (one step), click reaction on the surface (two steps), and reverse click reaction on the surface (two steps). The SAM structure is well studied to determine the SAM orientation, SAM arrangement, and ferrocene position within the SAM. Electron transfer kinetics have also been studied, which agree with the quality of each SAM. With the help of two anchoring groups and click-chemistry active functional groups, we have shown that the two molecules can be deposited by controlling the position of ferrocene at either end. We further investigated the involvement of the triazole five-membered ring in the electron transfer mechanism. We have found that a carbon spacer between ferrocene and triazole improves the SAM packing. This study enhances the understanding of tethering thiol and thiol acetate anchoring groups on gold by a controlled orientation, which may help in the development of functional molecular devices requiring two anchoring groups.

Deciphering the Orientation of the Aromatic Spacer Cation in Bilayer Perovskite Solar Cells through Spectroscopic Techniques.

Slowing the degradation of perovskite-based solar cells (PSCs) is of substantial interest. We engineered the surface by introducing a hydrophobic overlayer on a three-dimensional (3D) perovskite using fluorinated or nonfluorinated aryl ammonium cation spacers. The placement of a fluoroarene cation allows the formation of a bilayer structure, that is, layered/3D perovskites. By doing so, the surface hydrophobic character increases notably by the virtue of the perfluorinated benzene moiety. The fabricated devices thereof gave higher performance and longevity than control devices in addition to boosting reliability. The fluoro-phenethylammonium iodide (FPEAI)-based devices showed lower nonradiative carrier recombination. To decipher the orientation of the spacer cation in this bilayer structure, we probed the surface by polarization-modulated infrared reflection-absorption spectroscopy and noted substantial differences in the orientation due to the presence of fluorine substitution. We hypothesize that the stronger van der Waals interactions due to the higher electronegativity in FPEAI govern the orientation and performance enhancement and act as a barrier to moisture decomposition.

Enantiopure cryptophane derivatives: Synthesis and chiroptical properties.

This review addresses the synthesis of enantiopure cryptophane and the study of their chiroptical properties. Cryptophane derivatives represent an important class of macrocyclic compounds that can bind a large range of species in solution under different conditions. The overwhelming majority of these host molecules is chiral, and their chiroptical properties have been thoroughly investigated. The first part of this review is dedicated to the optical resolution and the synthesis of enantiopure cryptophane derivatives. In a second part, the study of the chiroptical properties of these molecular hosts by different techniques such as electronic and vibrational circular dichroism and Raman optical activity is detailed. These techniques allow the determination of the absolute configuration of cryptophane derivatives and provide useful information about their conformation in different conditions.

Comment on "Eppur si Muove: Proton Diffusion in Halide Perovskite Single Crystals": Eppur Non si Muove: A Critical Evaluation of Proton Diffusion in Halide Perovskite Single Crystals.

A recent report by Cahen and co-workers is examined that finds the diffusion constant for proton migration in methylammonium lead triiodide single crystals to be 2 × 105 -fold greater than that previously reported by Sadhu et al. By comparing the conversion of single crystals versus microcrystalline samples, it is concluded that proton diffusion in macroscopic single crystals is accelerated by the presence of defects acting as high-diffusivity paths.

Chirality induction to achiral molecules by silica-coated chiral molecular assemblies.

Hybrid silica-organic nanohelices are used to organize a large variety of nonchiral small organic molecules or inorganic anions to nanometer-sized assemblies. Such chiral organization of achiral molecules induces chiroptical properties as detected by vibrational or electronic circular dichroism (CD), as well as from circularly polarized luminescence (CPL).

Sensing a binding event through charge transport variations using an aromatic oligoamide capsule.

The selective binding properties of a 13-mer oligoamide foldamer capsule composed of 4 different aromatic subunits are reported. The capsule was designed to recognize dicarboxylic acids through multiple-point interactions owing to a combination of protonation/deprotonation events, H-bonding, and geometrical constraints imparted by the rigidity of the foldamer backbone. Compared to tartaric acid, binding of 2,2-difluorosuccinic acid or 2,2,3,3-tetrafluorosuccinic acid resulted in symmetry breaking due to deprotonation of only one of the two carboxylic acid groups of the encapsulated species as shown by NMR studies in solution and by single-crystal X-ray diffraction in the solid state. An analogous 14-mer foldamer capsule terminated with a thiol anchoring group was used to probe the complexation event in self-assembled monolayers on Au substrates. Ellipsometry and polarization-modulation infrared absorption-reflection spectroscopy studies were consistent with the formation of a single molecule layer of the foldamer capsule oriented vertically with respect to the surface. The latter underwent smooth complexation of 2,2-difluorosuccinic acid with deprotonation of one of the two carboxylic acid groups. A significant (80-fold) difference in the charge transport properties of the monolayer upon encapsulation of the dicarboxylic acid was evidenced from conducting-AFM measurements (S = 1.1 × 10-9 vs. 1.4 × 10-11 ohm-1 for the empty and complexed capsule, respectively). The modulation in conductivity was assigned to protonation of the aromatic foldamer backbone.

Molecular-scale spatio-chemical control of the activating-inhibitory signal integration in NK cells.

The role of juxtaposition of activating and inhibitory receptors in signal inhibition of cytotoxic lymphocytes remains strongly debated. The challenge lies in the lack of tools that allow simultaneous spatial manipulation of signaling molecules. To circumvent this, we produced a nanoengineered multifunctional platform with molecular-scale spatial control of ligands, which was applied to elucidate KIR2DL1-mediated inhibition of NKG2D signaling-receptors of natural killer cells. This platform was conceived by bimetallic nanodot patterning with molecular-scale registry, followed by a ternary functionalization with distinct moieties. We found that a 40-nm gap between activating and inhibitory ligands provided optimal inhibitory conditions. Supported by theoretical modeling, we interpret these findings as a consequence of the size mismatch and conformational flexibility of ligands in their spatial interaction. This highly versatile approach provides an important insight into the spatial mechanism of inhibitory immune checkpoints, which is essential for the rational design of future immunotherapies.

Loading Linear Arrays of CuII Inside Aromatic Amide Helices.

The very stable helices of 8-amino-2-quinolinecarboxylic acid oligoamides are shown to uptake CuII ions in their cavity through deprotonation of their amide functions with minimal alteration of their shape, unlike most metallo-organic structures which generally differ from their organic precursors. The outcome is the formation of intramolecular linear arrays of a defined number of CuII centers (up to sixteen in this study) at a 3 Šdistance, forming a molecular mimic of a metal wire completely surrounded by an organic sheath. The helices pack in the solid state so that the arrays of CuII extend intermolecularly. Conductive-AFM and cyclic voltammetry suggest that electrons are transported throughout the metal-loaded helices in contrast with hole transport observed for analogous foldamers devoid of metal ions.