Unraveling the Dynamic Molecular Motions of a Twin-Cavity Cage with Slow Configurational but Rapid Conformational Interconversions.

Featuring diverse structural motions/changes, dynamic molecular systems hold promise for executing complex tasks. However, their structural complexity presents formidable challenge in elucidating their kinetics, especially when multiple structural motions are intercorrelated. We herein introduce a twin-cavity cage that features interconvertible C3- and C1-configurations, with each configuration exhibiting interchangeable P- and M-conformations. This molecule is therefore composed of four interconnected chiral species (P)-C3, (M)-C3, (P)-C1, (M)-C1. We showcase an effective approach to decouple these sophisticated structural changes into two kinetically distinct pathways. Utilizing time-dependent 1H NMR spectroscopy at various temperatures, which disregards the transition between mirror-image conformations, we first determine the rate constant (kc) for the C3- to C1-configuration interconversion, while time-dependent circular dichroism spectroscopy at different temperatures quantifies the observed rate constant (kobs) of the ensemble of all the structural changes. As kobs ≫ ${{\rm { \gg }}}$ kc, it allows us to decouple the overall molecular motions into a slow configurational transformation and rapid conformational interconversions, with the latter further dissected into two independent conformational interchanges, namely (P)-C3 ← → ${ \mathbin{{\stackrel{\textstyle\rightarrow} { {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}} } }} }$ (M)-C3 and (P)-C1 ← → ${ \mathbin{{\stackrel{\textstyle\rightarrow} { {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}} } }} }$ (M)-C1. This work, therefore, sheds light on the comprehensive kinetic study of complex molecular dynamics, offering valuable insights for the rational design of smart dynamic materials for applications of sensing, separation, catalysis, molecular machinery, etc.

Spontaneous Symmetry Breaking of Achiral Molecules Leading to the Formation of Homochiral Superstructures that Exhibit Mechanoluminescence.

Chirality, with its intrinsic symmetry-breaking feature, is frequently utilized in the creation of acentric crystalline functional materials that exhibit intriguing optoelectronic properties. On the other hand, the development of chiral crystals from achiral molecules offers a solution that bypasses the need for enantiopure motifs, presenting a promising alternative and thereby expanding the possibilities of the self-assembly toolkit. Nevertheless, the rational design of achiral molecules that prefer spontaneous symmetry breaking during crystallization has so far been obscure. In this study, we present a series of six achiral molecules, demonstrating that when these conformationally flexible molecules adopt a cis-conformation and engage in multiple non-covalent interactions along a helical path, they collectively self-assemble into chiral superstructures consisting of single-handed supramolecular columns. When these homochiral supramolecular columns align in parallel, they form polar crystals that exhibit intense luminescence upon grinding or scraping. We therefore demonstrate our molecular design strategy could significantly increase the likelihood of symmetry breaking in achiral molecular synthons during self-assembly, offering a facile access to novel chiral crystalline materials with unique optoelectronic properties.

The inhibition of Aurora A kinase regulates phospholipid remodeling by upregulating LPCAT1 in glioblastoma.

Metabolic reprogramming is a common feature of glioblastoma (GBM) progression and metastasis. Altered lipid metabolism is one of the most prominent metabolic alterations in cancer. Understanding the links between phospholipid remodeling and GBM tumorigenesis may help develop new anticancer strategies and improve treatments to overcome drug resistance. We used metabolomic and transcriptomic analyses to systematically investigate metabolic and molecular changes in low-grade glioma (LGG) and GBM. We then re-established the reprogrammed metabolic flux and membrane lipid composition in GBM based on metabolomic and transcriptomic analyses. By inhibiting Aurora A kinase via RNA interference (RNAi) and inhibitor treatment, we investigated the effect of Aurora A kinase on phospholipid reprogramming LPCAT1 enzyme expression and GBM cell proliferation in vitro and in vivo. We found that GBM displayed aberrant glycerophospholipid and glycerolipid metabolism compared with LGG. Metabolic profiling indicated that fatty acid synthesis and uptake for phospholipid synthesis were significantly increased in GBM compared to LGG. The unsaturated phosphatidylcholine (PC) and phosphatidylethanolamine (PE) levels were significantly decreased in GBM compared to LGG. The expression level of LPCAT1, which is required for the synthesis of saturated PC and PE, was upregulated in GBM, and the expression of LPCAT4, which is required for the synthesis of unsaturated PC and PE, was downregulated in GBM. Notably, the inhibition of Aurora A kinase by shRNA knockdown and treatment with Aurora A kinase inhibitors such as Alisertib, AMG900, or AT9283 upregulated LPCAT1 mRNA and protein expression in vitro. In vivo, the inhibition of Aurora A kinase with Alisertib increased LPCAT1 protein expression. Phospholipid remodeling and a reduction in unsaturated membrane lipid components were found in GBM. Aurora A kinase inhibition increased LPCAT1 expression and suppressed GBM cell proliferation. The combination of Aurora kinase inhibition with LPCAT1 inhibition may exert promising synergistic effects on GBM.

Speech Recognition of Accented Mandarin Based on Improved Conformer.

The convolution module in Conformer is capable of providing translationally invariant convolution in time and space. This is often used in Mandarin recognition tasks to address the diversity of speech signals by treating the time-frequency maps of speech signals as images. However, convolutional networks are more effective in local feature modeling, while dialect recognition tasks require the extraction of a long sequence of contextual information features; therefore, the SE-Conformer-TCN is proposed in this paper. By embedding the squeeze-excitation block into the Conformer, the interdependence between the features of channels can be explicitly modeled to enhance the model's ability to select interrelated channels, thus increasing the weight of effective speech spectrogram features and decreasing the weight of ineffective or less effective feature maps. The multi-head self-attention and temporal convolutional network is built in parallel, in which the dilated causal convolutions module can cover the input time series by increasing the expansion factor and convolutional kernel to capture the location information implied between the sequences and enhance the model's access to location information. Experiments on four public datasets demonstrate that the proposed model has a higher performance for the recognition of Mandarin with an accent, and the sentence error rate is reduced by 2.1% compared to the Conformer, with only 4.9% character error rate.

A Pair of Interconverting Cages Formed from Achiral Precursors Spontaneously Resolve into Homochiral Conformers.

Without chiral induction the emergence of homochirality from achiral molecules is rather serendipitous, as the rationale is somewhat ambiguous. We herein provide a plausible solution. From achiral precursors are formed a pair of interconverting cage conformers that exhibit a C3 -axis as the only symmetry element. When their interconversion is impeded with intramolecular H-bonding, each conformer self-sorts into a homochiral crystal, which is driven by a helical network of multivalent intermolecular interactions during the self-assembly of homochiral cage conformers. As no chiral induction is involved throughout, we believe our study could enlighten the rational design for the emergence of homochirality with several criteria: 1) formation of a molecule without inversion center or mirror plane; 2) suppression of the enantiomeric interconversion, and introduction of multivalent interactions along the helical trajectory of screw symmetry within the resulting superstructure.

Circularly Polarized Laser Emission from Homochiral Superstructures based on Achiral Molecules with Conformal Flexibility.

Without external chiral intervention, it is a challenge to form homochirality from achiral molecules with conformational flexibility. We here report on a rational strategy that uses multivalent noncovalent interactions to clamp the molecular conformations of achiral D-A molecules. These interactions overcome the otherwise dominant dipole-dipole interactions and thus disfavor their symmetric antiparallel stacking. It in turn facilitates parallel packing, leading to spontaneous symmetry breaking during crystallization and thus the formation of homochiral conglomerates. When this emergent homochirality is coupled with optical gain characteristics of the molecules, the homochiral crystals are explored as excellent circularly polarized micro-lasers with low lasing threshold (16.4 µJ cm-2 ) and high dissymmetry factor glum (0.9). This study therefore provides a facile design strategy for supramolecular chiral materials and active laser ones without the necessity of intrinsic chiral element.

Spontaneous Resolution of Racemic Cage-Catenanes via Diastereomeric Enrichment at the Molecular Level and Subsequent Narcissistic Self-Sorting at the Supramolecular Level.

The spontaneous resolution of racemates, from natural compounds to artificial structures, has long been pursued to shed light on the origin of homochirality in life. Even though diverse synthetic systems have been elegantly devised to elaborate the underlying principles of spontaneous symmetry breaking, their complexity is still unparalleled to the natural masterpieces including DNA helix and proteins, which convey remarkable coalescence at both molecular and supramolecular levels. Here, we report on the spontaneous resolution of a pair of homochiral entities from a racemic mixture of a triply interlocked cage-catenane comprising 720 possible stereoisomers. This cage-catenane comprises six methyldithiane ring-containing linkers (denoted rac-2). As each methyldithiane ring has two chiral centers, it exhibits four possible diastereomers. These otherwise equimolar diastereomers are preferentially differentiated with the equatorial conformers over their axial analogues, leading to the dominant formation of (S, R)-2 and (R, S)-2, i.e., diastereomeric enrichment at the molecular level. This diastereomeric enrichment is unbiasedly transferred from precursor rac-2 to cage-catenane rac-4, from which a pair of homochirals (S, R)6-4 and (R, S)6-4 is narcissistically self-sorted upon crystallization. This powerful symmetry breaking is attributed to a supramolecular synergy of directional π-π stacking with the multivalency of erstwhile weak S···S contacts (with an unusual distance of 3.09 Å) that are cooperatively arranged in a helical fashion. This work highlights the attainability of complex homochiral entities by resorting to coalesced covalent and noncovalent contributions and therefore provides additional clues to the symmetry breaking of sophisticated yet well-defined architectures.

Long-Term Observation of the Quasi-3-Hour Large-Scale Traveling Ionospheric Disturbances by the Oblique-Incidence Ionosonde Network in North China.

The oblique-incidence ionosonde network in North China is a very unique system for regional ionospheric observation. It contains 5 transmitters and 20 receivers, and it has 99 ionospheric observation points between 22.40° N and 33.19° N geomagnetic latitudes. The data of the ionosonde network were used to investigate the statistical characteristics of the quasi-3-h large-scale traveling ionospheric disturbances (LSTIDs). From September 2009 to August 2011, 157 cases of the quiet-time LSTIDs were recorded; 110 cases traveled southward, 46 cases traveled southwestward and only 1 case traveled southeastward. The LSTIDs mainly appeared between 10:00 and 19:00 LT in the months from September to the following May. We compared the data of the Beijing, Mohe and Yakutsk digisondes and found that the LSTIDs are most likely to come from the northern auroral region. These LSTIDs may be induced by the atmospheric gravity waves (AGWs) and presented obvious seasonal and diurnal varying features, indicating that the thermospheric wind field has played an important role.

Single-Handed Double Helix and Spiral Platelet Formed by Racemate of Dissymmetric Cages.

Spontaneous deracemization has been used to separate homochiral domains from the racemic system. However, homochirality can only be referred to when the scales of these domains and systems are specified. To clarify this, we report self-assembly of racemates of dissymmetric cages DC-1 with a cone-shape propeller geometry, forming a centrosymmetric columnar crystalline phase (racemic at crystallographic level). Owing to their anisotropic geometry, the two enantiomers are packed in a frustrated fashion in this crystalline phase; single-handed double helices are observed (single-handedness at supramolecular level). The frustrated packing (layer continuity break-up) in turn facilitates screw dislocation during the crystal growth, forming left- or right-handed spiral platelets (symmetry-breaking at morphological level), although each platelet is composed of DC-1 racemates. The symmetry correlation between DC-1 molecules, the crystalline phase and spiral platelets, all exhibit C3 symmetry.

Controlled Hierarchical Self-Assembly of Catenated Cages.

Constructing hierarchical superstructures to achieve comparable complexity and functions to proteins with four-level hierarchy is challenging, which relies on the elaboration of novel building blocks with complex structures. We present a series of catenated cages with unique structural complexity and tailorability. The rational design was realized as such: A catenane of two symmetric cages (CSC), CSC-1, with all rigid imine panels was converted to a catenane of two dissymmetric cages (CDC), CDC-1, with two exterior flexible amine panels, and CDC-5 was tailored from CDC-1 by introducing an additional methyl group on each blade to increase lateral hindrance. CDC-1s with the most irregular and flexible configuration formed supramolecular dimers, which self-organized into 3D continuous wavelike plank with a three-level hierarchy, previously undiscovered by conventional building blocks. A drastically different 3D triclinic crystalline phase with a four-level hierarchy and trigonal phase with a three-level hierarchy were constructed of distorted CSC-1s and the most symmetric CDC-5s, respectively. The wavelike plank exhibited the lowest order, and the triclinic phase had a lower order than the trigonal phase which had the highest order. It correlates with the configuration of the primary structures, namely, the most disordered shape of CDC-1, the low-order configuration of CSC-1, and the most ordered geometry of CDC-5. The catenated cages with subtle structural differences therefore provide a promising platform for the search of emerging hierarchical superstructures that might be applied to proton conductivity, ferroelectricity, and catalysis.

Multimode Self-Oscillating Vesicle Transformers.

Engineering synthetic materials that mimic the complex rhythmic oscillatory behavior of living cells is a fundamental challenge in science and technology. Up to now, the reported synthetic model system still cannot compete with nature in oscillatory modes and amplitudes. Presented here is a novel alternating copolymer vesicle that exhibits drastic and multimode shape oscillations in real time, which are controlled by polymer concentrations and driven by the Belousov-Zhabotinsky oscillatory reaction, including swelling/deswelling, twisting/detwisting, stretching/shrinking, fusion/fission, and multiple division. Some of them, especially the fission oscillation, have not been observed before. In addition, the oscillation magnitude with regard to diameter is much larger than that of previously reported self-oscillating vesicles. Such a self-oscillating vesicle transformer would extend the complexity and capacity of membrane deformations in synthetic systems, approaching those of natural cells.

De Novo Construction of Catenanes with Dissymmetric Cages by Space-Discriminative Post-Assembly Modification.

Considerable efforts have been made to increase the topological complexity of mechanically interlocked molecules over the years. Three-dimensional catenated structures composed of two or several (usually symmetrical) cages are one representative example. However, owing to the lack of an efficient universal synthetic strategy, interlocked structures made up of dissymmetric cages are relatively rare. Since the space volume of the inner cavity of an interlocked structure is smaller than that outside it, we developed a novel synthetic approach with the voluminous reductant NaBH(OAc)3 that discriminates this space difference, and therefore selectively reduces the outer surface of a catenated dimer composed of two symmetric cages, thus yielding the corresponding catenane with dissymmetric cages. Insight into the template effect that facilitates the catenation of cages was provided by computational and experimental techniques.

Bioactive cell-like hybrids coassembled from (glyco)dendrimersomes with bacterial membranes.

A library of amphiphilic Janus dendrimers including two that are fluorescent and one glycodendrimer presenting lactose were used to construct giant dendrimersomes and glycodendrimersomes. Coassembly with the components of bacterial membrane vesicles by a dehydration-rehydration process generated giant cell-like hybrid vesicles, whereas the injection of their ethanol solution into PBS produced monodisperse nanometer size assemblies. These hybrid vesicles contain transmembrane proteins including a small membrane protein, MgrB, tagged with a red fluorescent protein, lipopolysaccharides, and glycoproteins from the bacterium Escherichia coli. Incorporation of two colored fluorescent probes in each of the components allowed fluorescence microscopy to visualize and demonstrate coassembly and the incorporation of functional membrane channels. Importantly, the hybrid vesicles bind a human galectin, consistent with the display of sugar moieties from lipopolysaccharides or possibly glycosylated membrane proteins. The present coassembly method is likely to create cell-like hybrids from any biological membrane including human cells and thus may enable practical application in nanomedicine.

Onion-like glycodendrimersomes from sequence-defined Janus glycodendrimers and influence of architecture on reactivity to a lectin.

A library of eight amphiphilic Janus glycodendrimers (GDs) with d-mannose (Man) headgroups, a known routing signal for lectin-mediated transport processes, was constructed via an iterative modular methodology. Sequence-defined variations of the Janus GD modulate the surface density and sequence of Man after self-assembly into multilamellar glycodendrimersomes (GDSs). The spatial mode of Man presentation is decisive for formation of either unilamellar or onion-like GDS vesicles. Man presentation and Janus GD concentration determine GDS size and number of bilayers. Beyond vesicle architecture, Man topological display affects kinetics and plateau level of GDS aggregation by a tetravalent model lectin: the leguminous agglutinin Con A, which is structurally related to endogenous cargo transporters. The agglutination process was rapid, efficient, and readily reversible for onion-like GDSs, demonstrating their value as versatile tools to explore the nature of physiologically relevant glycan/lectin pairing.

A Role of Endogenous Progesterone in Stroke Cerebroprotection Revealed by the Neural-Specific Deletion of Its Intracellular Receptors.

Treatment with progesterone protects the male and female brain against damage after middle cerebral artery occlusion (MCAO). However, in both sexes, the brain contains significant amounts of endogenous progesterone. It is not known whether endogenously produced progesterone enhances the resistance of the brain to ischemic insult. Here, we used steroid profiling by gas chromatography-tandem mass spectrometry (GC-MS/MS) for exploring adaptive and sex-specific changes in brain levels of progesterone and its metabolites after MCAO. We show that, in the male mouse brain, progesterone is mainly metabolized via 5α-reduction leading to 5α-dihydroprogesterone (5α-DHP), also a progesterone receptor (PR) agonist ligand in neural cells, then to 3α,5α-tetrahydroprogesterone (3α,5α-THP). In the female mouse brain, levels of 5α-DHP and 3α,5α-THP are lower and levels of 20α-DHP are higher than in males. After MCAO, levels of progesterone and 5α-DHP are upregulated rapidly to pregnancy-like levels in the male but not in the female brain. To assess whether endogenous progesterone and 5α-DHP contribute to the resistance of neural cells to ischemic damage, we inactivated PR selectively in the CNS. Deletion of PR in the brain reduced its resistance to MCAO, resulting in increased infarct volumes and neurological deficits in both sexes. Importantly, endogenous PR ligands continue to protect the brain of aging mice. These results uncover the unexpected importance of endogenous progesterone and its metabolites in cerebroprotection. They also reveal that the female reproductive hormone progesterone is an endogenous cerebroprotective neurosteroid in both sexes.SIGNIFICANCE STATEMENT The brain responds to injury with protective signaling and has a remarkable capacity to protect itself. We show here that, in response to ischemic stroke, levels of progesterone and its neuroactive metabolite 5α-dihydroprogesterone are upregulated rapidly in the male mouse brain but not in the female brain. An important role of endogenous progesterone in cerebroprotection was demonstrated by the conditional inactivation of its receptor in neural cells. These results show the importance of endogenous progesterone, its metabolites, and neural progesterone receptors in acute cerebroprotection after stroke. This new concept could be exploited therapeutically by taking into account the progesterone status of patients and by supplementing and reinforcing endogenous progesterone signaling for attaining its full cerebroprotective potential.

Unraveling functional significance of natural variations of a human galectin by glycodendrimersomes with programmable glycan surface.

Surface-presented glycans (complex carbohydrates) are docking sites for adhesion/growth-regulatory galectins within cell-cell/matrix interactions. Alteration of the linker length in human galectin-8 and single-site mutation (F19Y) are used herein to illustrate the potential of glycodendrimersomes with programmable glycan displays as a model system to reveal the functional impact of natural sequence variations in trans recognition. Extension of the linker length slightly reduces lectin capacity as agglutinin and slows down aggregate formation at low ligand surface density. The mutant protein is considerably less active as agglutinin and less sensitive to low-level ligand presentation. The present results suggest that mimicking glycan complexity and microdomain occurrence on the glycodendrimersome surface can provide key insights into mechanisms to accomplish natural selectivity and specificity of lectins in structural and topological terms.

Self-assembly of amphiphilic Janus dendrimers into uniform onion-like dendrimersomes with predictable size and number of bilayers.

A constitutional isomeric library synthesized by a modular approach has been used to discover six amphiphilic Janus dendrimer primary structures, which self-assemble into uniform onion-like vesicles with predictable dimensions and number of internal bilayers. These vesicles, denoted onion-like dendrimersomes, are assembled by simple injection of a solution of Janus dendrimer in a water-miscible solvent into water or buffer. These dendrimersomes provide mimics of double-bilayer and multibilayer biological membranes with dimensions and number of bilayers predicted by the Janus compound concentration in water. The simple injection method of preparation is accessible without any special equipment, generating uniform vesicles, and thus provides a promising tool for fundamental studies as well as technological applications in nanomedicine and other fields.

From structure to function via complex supramolecular dendrimer systems.

This tutorial review summarizes strategies elaborated for the discovery and prediction of programmed primary structures derived from quasi-equivalent constitutional isomeric libraries of self-assembling dendrons, dendrimers and dendronized polymers. These libraries demonstrate an 82% predictability, defined as the percentage of similar primary structures resulting in at least one conserved supramolecular shape with internal order. A combination of structural and retrostructural analysis that employs methodologies transplanted from structural biology, adapted to giant supramolecular assemblies was used for this process. A periodic table database of programmed primary structures was elaborated and used to facilitate the emergence of a diversity of functions in complex dendrimer systems via first principles. Assemblies generated by supramolecular and covalent polymer backbones were critically compared. Although by definition complex functional systems cannot be designed, this tutorial hints to a methodology based on database analysis principles to facilitate design principles that may help to mediate an accelerated emergence of chemical, physical and most probably also societal, political and economic complex systems on a shorter time scale and lower cost than by the current methods. This tutorial review is limited to the simplest, synthetically most accessible self-assembling minidendrons, minidendrimers and polymers dendronized with minidendrons that are best analyzed and elucidated at molecular, supramolecular and theoretical levels, and most used in other laboratories. These structures are all interrelated, and their principles expand in a simple way to their higher generations.

Glycodendrimersomes from Sequence-Defined Janus Glycodendrimers Reveal High Activity and Sensor Capacity for the Agglutination by Natural Variants of Human Lectins.

A library of eight amphiphilic Janus glycodendrimers (Janus-GDs) presenting D-lactose (Lac) and a combination of Lac with up to eight methoxytriethoxy (3EO) units in a sequence-defined arrangement was synthesized via an iterative modular methodology. The length of the linker between Lac and the hydrophobic part of the Janus-GDs was also varied. Self-assembly by injection from THF solution into phosphate-buffered saline led to unilamellar, monodisperse glycodendrimersomes (GDSs) with dimensions predicted by Janus-GD concentration. These GDSs provided a toolbox to measure bioactivity profiles in agglutination assays with sugar-binding proteins (lectins). Three naturally occurring forms of the human adhesion/growth-regulatory lectin galectin-8, Gal-8S and Gal-8L, which differ by the length of linker connecting their two active domains, and a single amino acid mutant (F19Y), were used as probes to study activity and sensor capacity. Unpredictably, the sequence of Lac on the Janus-GDs was demonstrated to determine bioactivity, with the highest level revealed for a Janus-GD with six 3EO groups and one Lac. A further increase in Lac density was invariably accompanied by a substantial decrease in agglutination, whereas a decrease in Lac density resulted in similar or lower bioactivity and sensor capacity. Both changes in topology of Lac presentation of the GDSs and seemingly subtle alterations in protein structure resulted in different levels of bioactivity, demonstrating the presence of regulation on both GDS surface and lectin. These results illustrate the applicability of Janus-GDs to dissect structure-activity relationships between programmable cell surface models and human lectins in a highly sensitive and physiologically relevant manner.

Dissecting molecular aspects of cell interactions using glycodendrimersomes with programmable glycan presentation and engineered human lectins.

Glycodendrimersomes with programmable surface display of glycan, together with artificially engineered galectins, were used to understand the physiological significance of human lectins with homodimeric and tandem-repeat-type displays. The mode of topological surface presentation and the density of glycan affected vesicle aggregation mediated by multivalent carbohydrate-protein interactions. The cross-linking capacity of homodimeric lectins was enhanced by covalent connection of the two carbohydrate-binding sites. These findings highlight the value of glycodendrimersomes as versatile cell membrane mimetics, and assays provide diagnostic tools for protein functionality. This work also provides guidelines for the design of cell separators, bioactive matrices, bioeffectors, and other biomedical applications.