Molecules that exhibit emission in the solid state, especially those known as aggregation-induced emission (AIE) chromophores, have found applications in areas as varied as light-emitting diodes and ...biological sensors. Despite numerous studies, the mechanism of fluorescence quenching in AIE chromophores is still not completely understood. To this end, much interest has focused on understanding the low-frequency vibrational dynamics of prototypical systems, such as tetraphenylethylene (TPE), in the hope that such studies would provide more general principles toward the design of new sensors and electronic materials. We hereby show that a perdeuterated TPE-based metal–organic framework (MOF) serves as an excellent platform for studying the low-energy vibrational modes of AIE-type chromophores. In particular, we use solid-state 2H and 13C NMR experiments to investigate the phenyl ring dynamics of TPE cores that are coordinatively trapped inside a MOF and find a phenyl ring flipping energy barrier of 43(6) kJ/mol. DFT calculations are then used to deconvolute the electronic and steric contributions to this flipping barrier. Finally, we couple the NMR and DFT studies with variable-temperature X-ray diffraction experiments to propose that both the ethylenic CC bond twist and the torsion of the phenyl rings are important for quenching emission in TPE, but that the former may gate the latter. To conclude, we use these findings to propose a set of design criteria for the development of tunable turn-on porous sensors constructed from AIE-type molecules, particularly as applied to the design of new multifunctional MOFs.
Nutrimiromics studies the influence of the diet on the modification of gene expression due to epigenetic processes related to microRNAs (miRNAs), which may affect the risk for the development of ...chronic diseases. miRNAs are a class of non-coding endogenous RNA molecules that are usually involved in post-transcriptional gene silencing by inducing mRNA degradation or translational repression by binding to a target messenger RNA. They can be controlled by environmental and dietary factors, particularly by isolated nutrients or bioactive compounds, indicating that diet manipulation may hold promise as a therapeutic approach in modulating the risk of chronic diseases. This review summarizes the evidence regarding the influence of nutrients and bioactive compounds on the expression of miRNAs related to inflammation and chronic disease in several models (cell culture, animal models, and human trials).
Mineral dust particles represent the most abundant component of atmospheric aerosol in terms of dry mass. They play a key role in climate and climate change, so the study of their emission processes ...is of utmost importance. Measurements of dust emission into the atmosphere are scarce, so that the dust load is generally estimated using models. It is known that the emission process can generate strong atmospheric electric fields. Starting from the data we acquired in the Sahara desert, here, we show for the first time that depending on the relative humidity conditions, electric fields contribute to increase up to a factor of 10 the amount of particles emitted into the atmosphere. This means that electrical forces and humidity are critical quantities in the dust emission process and should be taken into account in climate and circulation models to obtain more realistic estimations of the dust load in the atmosphere.
Key Points
The tight interrelation between the dust‐lifting process and atmospheric electric field is shown
The role of the relative humidity is demonstrated
Electric forces contribute to the entrainment of dust in the atmosphere
Organochalcogen−nitrogen heterocycles such as the 1,2,5-chalcogenadiazoles have a distinct tendency to establish intermolecular links in the solid state through secondary bonding interactions E···N ...(E = S, Se, Te). The association of these molecules was examined in detail using relativistic density functional theory. Although there is an important electrostatic component, the interaction between these molecules is dominated by contributions arising from orbital mixing, which can be interpreted as the donation of a nitrogen lone pair into the chalcogen-centered antibonding orbitals. Because of its more polar character and lower-lying antibonding orbitals, the tellurium derivatives possess the strongest association energies; these are so large that the binding strength is comparable to that of some hydrogen bonds. In the absence of steric constraints, telluradiazoles associate in a coplanar fashion forming ribbon polymers. However, bulky susbstituents could be used to direct the formation of either helical chains or discrete dimers. In addition to its strength, the coplanar dimer is characterized by being rigid, yet no activation barrier is expected for the association/dissociation process. These attributes strongly indicate that tellurium−nitrogen heterocycles have great potential as building blocks in supramolecular architecture.
Triple pnictogen bonding refers to the ability of a pnictogen atom to engage in three simultaneous pnictogen bonds (PnBs) to a complementary partner through a single pnictogen atom. This ...supramolecular strategy was recently introduced as a unique facet of pnictogen bonding as compared to other named supramolecular interactions. Here, the ability of bismuth to participate in this phenomenon is demonstrated using Bi((NC9H7)3CH3). The study reveals that Bi engages in stronger PnBs than the analogous Sb system. The results have been contrasted with Bi systems that form strong coordination bonds, and analysis of the electron density along the bond path reveals key differences. The solution behavior of these newly synthesized supramolecules were studied by PFGSE NMR spectroscopy and they are found to remain intact in solution. Molecular design strategies that allow for triple pnictogen bonding should find use in the fields of molecular recognition and crystal engineering.
The remarkable effect that secondary bonding interactions can have on the macroscopic properties of a material is illustrated by two polymorphs of the title compound. The phase which is most stable ...under ambient pressure and temperature consists of puckered supramolecular ribbon polymers assembled by Te--N secondary bonding interactions and displays a characteristic red-orange color. A second yellow phase consists of ribbons with alternating short and long intermolecular Te--N secondary bonding distances and is metastable; at 127 °C the material undergoes an exothermic irreversible transition to the red polymorph. A third phase consists of pyridine-solvated supramolecular dimers; it is also yellow and transforms into the red phase after the crystals effloresce. Computational DFT studies indicate that the observed changes in optical properties are related to intermolecular mixing of π orbitals enabled by the supramolecular interactions and the symmetry of the supramolecular synthon.
Wind‐formed features are abundant in Oxia Planum (Mars), the landing site of the 2022 ExoMars mission, which shows geological evidence for a past wet environment. Studies of aeolian bedforms at the ...landing site were focused on assessing the risk for rover trafficability, however their potential in recording climatic fluctuations has not been explored. Here we show that the landing site experienced multiple climatic changes in the Amazonian, which are recorded by an intriguing set of ridges that we interpret as Periodic Bedrock Ridges (PBRs). Clues for a PBR origin result from ridge regularity, defect terminations, and the presence of preserved megaripples detaching from the PBRs. PBR orientation differs from superimposed transverse aeolian ridges pointing toward a major change in wind regime. Our results provide constrains on PBR formation mechanisms and offer indications on paleo winds that will be crucial for understanding the landing site geology.
Plain Language Summary
Oxia Planum on Mars is the landing site for the ExoMars 2022 mission. The region likely hosted a standing body of water, but the effect of the wind was also important in shaping the landscape. In this study, we first describe a set of linear ridges that, in our interpretation, were sculpted by the wind in a more recent past. We also show that the wind that formed the ridges (Periodic Bedrock Ridges) was blowing from a different direction than the ones that formed younger ripples on top, suggesting a complex geological history of wind erosion and deposition that will be further investigated during the ExoMars mission.
Key Points
We present the first evidence for a periodic bedrock ridge (PBRs) pattern from the ExoMars 2022 landing site
Formative paleowind directions are extrapolated from PBRs and transverse aeolian ridges
Evidence for an Amazonian change in the wind regime are provided
The manufacture and characterization of gluten-free spaghetti based on maize flour and different vegetable flours (artichoke, asparagus, pumpkin, zucchini, tomato, yellow pepper, red pepper, green ...pepper, carrot, broccoli, spinach, eggplant and fennel) were addressed in this study. The screening of the vegetable flours showed that homogeneity, color, fibrous, taste and odor were the parameters that have most influenced the overall quality of the dry spaghetti. The spaghetti added with yellow pepper flour was chosen for further analysis because of its highest sensory quality; in contrast, it recorded low carotenoids content due to the high temperature of the drying process (cycle named as HTDC). Therefore, an optimization of the drying cycle was performed (lower temperature) on the yellow pepper flour (cycle named as LTDC) that resulted in an increase of the carotenoids content. Although the spaghetti with low temperature yellow pepper flour had a higher cooking loss and lower instrumental hardness when compared to the spaghetti made with only maize flour (CTRL) it however had a significantly higher protein and dietary fiber content. Moreover there was no significant difference in the amount of glucose released during in vitro digestion for this spaghetti sample with respect to the CTRL sample.
► Manufacture and characterization of gluten-free spaghetti added with vegetable flour. ► Among the enriched spaghetti, that with the yellow pepper was sensorially the best. ► The yellow pepper flour was produced with two different drying processes. ► The low temperature yellow pepper flour had higher content of the antioxidant components. ► P_LTYP (Pasta with Low Temperature Yellow Pepper) had higher dietary fibers content.
1,2,5-Telluradiazole rings have a remarkably strong tendency toward association through Te−N secondary bonding interactions in the solid state. The reproducibility of the bond lengths and angles in ...the known crystal structures allowed the parametrization of an anharmonic force field to accommodate both the inter- and intramolecular Te−N bonds. The new parameters were tested against published crystal structures and were able to accurately reproduce the experimentally observed geometries. The incorporation of these parameters into a molecular mechanics force field enables the modeling of large and complex structures with significantly less computational effort than Hartree−Fock (HF) or density functional theory (DFT) methods. Simple modifications to the parameter set allowed the modeling of the structures of acyclic tellurium diamides. A series of 4,7-disubstituted benzo-2,1,3-telluradiazoles were modeled to probe the steric barrier of dimerization; only the groups with large spherical bulks such as t-butyl, trimethylsilyl, and adamantyl were able to destabilize the dimers. Modeling based on bifunctional building blocks suggests strategies for the construction of novel two- and three-dimensional supramolecular architectures.
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