Articles de revues : « Heterochiral complex »

1

Kabza, Adam M., Brian E. Young, Nandini Kundu et Jonathan T. Sczepanski. « Heterochiral nucleic acid circuits ». Emerging Topics in Life Sciences 3, n^o 5 (28 août 2019) : 501–6. http://dx.doi.org/10.1042/etls20190102.

Texte intégral

Résumé :

The programmability of DNA/RNA-based molecular circuits provides numerous opportunities in the field of synthetic biology. However, the stability of nucleic acids remains a major concern when performing complex computations in biological environments. Our solution to this problem is l-(deoxy)ribose nucleic acids (l-DNA/RNA), which are mirror images (i.e. enantiomers) of natural d-nucleotides. l-oligonucleotides have the same physical and chemical properties as their natural counterparts, yet they are completely invisible to the stereospecific environment of biology. We recently reported a novel strand-displacement methodology for transferring sequence information between oligonucleotide enantiomers (which are incapable of base pairing with each other), enabling bio-orthogonal l-DNA/RNA circuits to be easily interfaced with living systems. In this perspective, we summarize these so-called ‘heterochiral’ circuits, provide a viewpoint on their potential applications in synthetic biology, and discuss key problems that must be solved before achieving the ultimate goal of the engineering complex and reliable functionality.

Styles APA, Harvard, Vancouver, ISO, etc.

2

Komiya, Naruyoshi, Takeharu Kageyama, Masaya Naito et Takeshi Naota. « A clothes-peg-shaped binucleartrans-bis(2-aminotroponato)palladium(II) complex bearing pentamethylene spacers ». Acta Crystallographica Section C Crystal Structure Communications 69, n^o 5 (23 avril 2013) : 503–5. http://dx.doi.org/10.1107/s0108270113004484.

Texte intégral

Résumé :

rac-Bis{μ-trans-2,2′-[pentane-1,5-diylbis(azanediyl)]ditroponato}dipalladium(II), [Pd2(C19H20N2O2)2], has been synthesized and fully characterized using single-crystal X-ray diffraction,1H NMR, FT–IR and mass spectroscopy. Thetranscoordination, vaulted structure andanticonformation have been unequivocally established from the X-ray diffraction studies. This is the first example of a bis(aminotroponato)palladium complex. In the crystalline state, the molecule has twofold symmetry and each molecular unit undergoes intermolecular offset π-stacking of the tropone rings to afford heterochiral interpenetrating dimers that are aligned in a lamellar manner with a herringbone packing motif.

Styles APA, Harvard, Vancouver, ISO, etc.

3

Bringmann, Gerhard, Doris Feineis, Ralph Brückner, Eva-Maria Peters et Karl Peters. « 2-Hexanoyl-1-tribromomethyl-1,2,3,4-tetrahydro-β-carboline : Crystal Structure Analysis of a Potent Inhibitor of Complex I of Mitochondrial Respiration ». Zeitschrift für Naturforschung B 55, n^o 1 (1 janvier 2000) : 94–99. http://dx.doi.org/10.1515/znb-2000-0115.

Texte intégral

Résumé :

The molecular structure of the title compound 2-hexanoyl-1-tribromomethyl-1,2,3,4-tetra-hydro-β-carboline (3), a potent inhibitor of complex I of the mammalian mitochondrial respiratory chain, has been studied by single-crystal X-ray diffraction analysis. In the crystal, two heterochiral molecules of 3 (i.e., one R- and one S-configured molecule each) were found to be connected with one other in pairs via two intermolecular hydrogen bonds [O(215) ··· H(212)′ and O(215)′ ··· H(212)] to form an overall achiral ‘dimeric’ subunit

Styles APA, Harvard, Vancouver, ISO, etc.

4

Jiao, Luyang, Mengying Du, Yameng Hou, Yuan Ma et Xianglei Kong. « Homochiral or Heterochiral : A Systematic Study of Threonine Clusters Using a FT ICR Mass Spectrometer ». Symmetry 14, n^o 1 (6 janvier 2022) : 86. http://dx.doi.org/10.3390/sym14010086.

Texte intégral

Résumé :

The strong chiral preferences of some magic clusters of amino acids have attracted continually increasing interests due to their unique structures, properties and possible roles in homochirogenesis. However, how chirality can influence the generation and stability of cluster ions in a wild range of cluster sizes is still unknown for most amino acids. In this study, the preference for threonine clusters to form homochiral and heterochiral complex ions has been investigated by electrospray ionization (ESI) mass spectrometry. Abundant cluster [Thrn+mH]m+ ions (7 ≤ n ≤ 78, 1 ≤ m ≤ 5) have been observed for both samples of enantiopure (100% L) and racemic (50:50 L:D) threonine solutions. Further analyses of the spectra show that the [Thr14+2H]2+ ion is characterized by its most outstanding homochiral preference, and [Thr7+H]+ and [Thr8+H]+ ions also clearly exhibit their homochiral preferences. Although most of the triply charged clusters (20 ≤ n ≤ 36) are characterized by heterochiral preferences, the quadruply charged [Thrn+4H]4+ ions (40 ≤ n ≤ 59) have no obvious chiral preference in general. On the other hand, a weak homochiral preference exists for most of the quintuply charged ions observed in the experiment.

Styles APA, Harvard, Vancouver, ISO, etc.

5

Fossey, John S., Ryosuke Matsubara, Hiroshi Kiyohara et Shū Kobayashi. « Heterochiral Triangulo Nickel Complex as Evidence of a Large Positive Nonlinear Effect in Catalysis ». Inorganic Chemistry 47, n^o 3 (février 2008) : 781–83. http://dx.doi.org/10.1021/ic7017727.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

6

Roithová, Jana. « Diastereoisomeric proton-bound complexes of 1,5-diaza-cis-decalin in the gas phase ». Collection of Czechoslovak Chemical Communications 74, n^o 2 (2009) : 243–54. http://dx.doi.org/10.1135/cccc2008185.

Texte intégral

Résumé :

Diastereoisomeric proton-bound complexes of 1,5-diaza-cis-decalin (1) with butan-2-amine (2) are studied by means of the DFT calculations and mass spectrometry. The calculations reveal that 2 is bound via proton to only one nitrogen atom of the bicyclic base 1. The homochiral complex is favored by about 4 kJ/mol over the heterochiral complex. For a more loosely bound ion-pair complex [(1H)I(2H)]+ of the protonated bases 1 and 2 with an iodine counterion the energy difference drops to about 2 kJ/mol. Chiral effects in the formation of [(1)H(2)]+ are studied by the collision-induced dissociation of [(1H)I(2H)]+ generated by the electrospray ionization of the solution of [1·Cu(OH)I] and 2 in acetonitrile. The dominant fragmentation of [(1H)I(2H)]+ leads to 1·H+ and 2·HI, which is at small collision energies accompanied by the elimination of HI leading to the desired [(1)H(2)]+ ion. The chiral effect of 1.2 is determined in favor for the formation of the homochiral complex [(1)H(2)]+.

Styles APA, Harvard, Vancouver, ISO, etc.

7

Ragland, Beau, et Lianjun Wu. « Characteristic Analysis of Heterochiral TCP Muscle as a Extensile Actuator for Soft Robotics Applications ». Actuators 12, n^o 5 (28 avril 2023) : 189. http://dx.doi.org/10.3390/act12050189.

Texte intégral

Résumé :

A soft actuator is an essential component in a soft robot that enables it to perform complex movements by combining different fundamental motion modes. One type of soft actuator that has received significant attention is the twisted and coiled polymer artificial muscle (TCP actuator). Despite many recent advancements in TCP actuator research, its use as an extensile actuator is less common in the literature. This works introduces the concept of using TCP actuators as thermal-driven extensile actuators for robotics applications. The low-profile actuator can be easily fabricated to offer two unique deformation capabilities. Results from the characterization indicate that extensile actuators, made with various rod diameters and under different load conditions, display remarkable elongation deformation. Additionally, a proof-of-concept soft-earthworm robot was developed to showcase the potential application of the extensile actuator and to demonstrate the benefits of combining different types of motion modes.

Styles APA, Harvard, Vancouver, ISO, etc.

8

Matveevskaya, Vladislava, Dmitry Pavlov et Andrei Potapov. « Iridium(III) and Rhodium(III) Half-Sandwich Coordination Compounds with 11H-Indeno[1,2-b]quinoxalin-11-one Oxime : A Case of Spontaneous Resolution of Rh(III) Complex ». Inorganics 10, n^o 11 (25 octobre 2022) : 179. http://dx.doi.org/10.3390/inorganics10110179.

Texte intégral

Résumé :

Two half-sandwich iridium(III) and rhodium(III) complexes with 11H-indeno[1,2-b]quinoxalin-11-one oxime (IQ-1) ligand were prepared by the reaction of the proligand with [M(Cp*)Cl2]2 (M = Ir, Rh) dimers. The reaction between IQ-1 and [Ir(Cp*)Cl2]2 in methanol gave the complex [Ir(Cp*)(IQ-1)Cl] (1), which crystallized in a centrosymmetric space group as a true racemate. Whereas complex [Rh(Cp*)(IQ-1)Cl] (2) in the form of a racemic conglomerate was obtained by the reaction of [Rh(Cp*)Cl2]2 and IQ-1 in methanol. The crystal structures of complexes 1 and 2 (R and S enantiomers) were determined by X-ray diffraction analysis, and the structural features were compared in order to understand the structural factors leading to the spontaneous enantiomer resolution of the rhodium(III) complex. In the crystal packing of 1, intermolecular C–H···C contacts between a pair of enantiomers link the molecules into centrosymmetric dimers and lead to the formation of heterochiral crystals of 1. In contrast, the intramolecular contacts CH···Cl and CH···C in complex 2 bind all three ligands around the chiral Rh(III) metal center. In addition, a combination of intermolecular CH···O and CH···C contacts leads to the formation of a homochiral supramolecular structure. These interactions altogether reinforce the spontaneous resolution in complex 2.

Styles APA, Harvard, Vancouver, ISO, etc.

9

Kazemi, Zahra, Hadi Amiri Rudbari, Mehdi Sahihi, Valiollah Mirkhani, Majid Moghadam, Shahram Tangestaninejad, Iraj Mohammadpoor-Baltork et Abolghasem Abbasi Kajani. « New homochiral and heterochiral Mo(VI) complex from racemic ligand : Synthesis, X-ray structure, diastereomers separation and biological activities ». Polyhedron 170 (septembre 2019) : 70–85. http://dx.doi.org/10.1016/j.poly.2019.05.021.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

10

Řezanka, Tomáš, Andrea Palyzová, Milada Vítová, Tomáš Brányik, Markéta Kulišová et Jarošová Kolouchová Irena. « Structural Characterization of Mono- and Dimethylphosphatidylethanolamines from Various Organisms Using a Complex Analytical Strategy including Chiral Chromatography ». Symmetry 14, n^o 3 (19 mars 2022) : 616. http://dx.doi.org/10.3390/sym14030616.

Texte intégral

Résumé :

Two minor phospholipids, i.e., mono- and/or dimethylphosphatidylethanolamines, are widespread in many organisms, from bacteria to higher plants and animals. A molecular mixture of methyl-PE and dimethyl-PE was obtained from total lipids by liquid chromatography and further identified by mass spectrometry. Total methyl-PE and dimethyl-PE were cleaved by phospholipase C, and the resulting diacylglycerols, in the form of acetyl derivatives, were separated into alkyl-acyl, alkenyl-acyl, and diacylglycerols. Reversed-phase LC/MS allowed dozens of molecular species to be identified and further analyzed. This was performed on a chiral column, and identification by tandem positive ESI revealed that diacyl derivatives from all four bacteria were mixtures of both R and S enantiomers. The same applied to alkenyl-acyl derivatives of anaerobic bacteria. Analysis thus confirmed that some bacteria biosynthesize phospholipids having both sn-glycerol-3-phosphate and sn-glycerol-1-phosphate as precursors. These findings were further supported by data already published in GenBank. The use of chiral chromatography made it possible to prove that both enantiomers of glycerol phosphate of some molecular species of mono- and dimethylphosphatidylethanolamines are present. The result of the analysis can be interpreted that the cultured bacteria do not have homochiral membranes but, on the contrary, have an asymmetric, i.e., heterochiral membranes.

Styles APA, Harvard, Vancouver, ISO, etc.

11

Fox, Allison C., Jason D. Boettger, Eve L. Berger et Aaron S. Burton. « The Role of the CuCl Active Complex in the Stereoselectivity of the Salt-Induced Peptide Formation Reaction : Insights from Density Functional Theory Calculations ». Life 13, n^o 9 (23 août 2023) : 1796. http://dx.doi.org/10.3390/life13091796.

Texte intégral

Résumé :

The salt-induced peptide formation (SIPF) reaction is a prebiotically plausible mechanism for the spontaneous polymerization of amino acids into peptides on early Earth. Experimental investigations of the SIPF reaction have found that in certain conditions, the l enantiomer is more reactive than the d enantiomer, indicating its potential role in the rise of biohomochirality. Previous work hypothesized that the distortion of the CuCl active complex toward a tetrahedral-like structure increases the central chirality on the Cu ion, which amplifies the inherent parity-violating energy differences between l- and d-amino acid enantiomers, leading to stereoselectivity. Computational evaluations of this theory have been limited to the protonated–neutral l + l forms of the CuCl active complex. Here, density functional theory methods were used to compare the energies and geometries of the homochiral (l + l and d + d) and heterochiral (l + d) CuCl–amino acid complexes for both the positive–neutral and neutral–neutral forms for alanine, valine, and proline. Significant energy differences were not observed between different chiral active complexes (i.e., d + d, l + l vs. l + d), and the distortions of active complexes between stereoselective systems and non-selective systems were not consistent, indicating that the geometry of the active complex is not the primary driver of the observed stereoselectivity of the SIPF reaction.

Styles APA, Harvard, Vancouver, ISO, etc.

12

Mandal, K., M. Uppalapati, D. Ault-Riche, J. Kenney, J. Lowitz, S. S. Sidhu et S. B. H. Kent. « Chemical synthesis and X-ray structure of a heterochiral {D-protein antagonist plus vascular endothelial growth factor} protein complex by racemic crystallography ». Proceedings of the National Academy of Sciences 109, n^o 37 (27 août 2012) : 14779–84. http://dx.doi.org/10.1073/pnas.1210483109.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

13

Jena, Himanshu Sekhar. « Effect of cooperative non-covalent interactions on the solid state heterochiral self-assembly : The concepts of isotactic and syndiotactic arrangements in coordination complex ». Inorganica Chimica Acta 410 (janvier 2014) : 156–70. http://dx.doi.org/10.1016/j.ica.2013.10.035.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

14

Wyszko, Eliza, Mariusz Popenda, Dorota Gudanis, Joanna Sarzyńska, Agnieszka Belter, Patrick Perrigue, Paweł Skowronek, Katarzyna Rolle et Jan Barciszewski. « The model structure of the hammerhead ribozyme formed by RNAs of reciprocal chirality ». Bioscience Reports, 22 décembre 2020. http://dx.doi.org/10.1042/bsr20203424.

Texte intégral

Résumé :

RNA-based tools are frequently used to modulate gene expression in living cells. However, the stability and effectiveness of such RNA-based tools is limited by cellular nuclease activity. One way to increase RNA’s resistance to nucleases is to replace its D-ribose backbone with L-ribose isomers. This modification changes chirality of an entire RNA molecule to L-form giving it more chance of survival when introduced into cells. Recently, we have described the activity of left-handed hammerhead ribozyme (L-Rz, L-HH) that can specifically hydrolyze RNA with the opposite chirality at a predetermined location. To understand the structural background of the RNA specific cleavage in a heterochiral complex, we used circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy as well as performed molecular modelling and dynamics simulations of homo- and heterochiral RNA complexes. The active ribozyme-target heterochiral complex showed a mixed chirality as well as low field imino proton NMR signals. We modelled the three dimensional structures of the oligoribonucleotides with their ribozyme counterparts of reciprocal chirality. L- or D-ribozyme formed a stable, homochiral helix 2, and two short double heterochiral helixes 1 and 3 of D- or L-RNA strand thorough irregular Watson-Crick base pairs. The formation of the heterochiral complexes is supported by the result of simulation molecular dynamics. These new observations suggest that L-catalytic nucleic acids can be used as tools in translational biology and diagnostics.

Styles APA, Harvard, Vancouver, ISO, etc.

15

Sun, Ke, Sicong Li, Bowen Zheng, Yanlei Zhu, Tongyue Wang, Mingfu Liang, Yue Yao et al. « Accurate de novo design of heterochiral protein–protein interactions ». Cell Research, 14 août 2024. http://dx.doi.org/10.1038/s41422-024-01014-2.

Texte intégral

Résumé :

AbstractAbiotic d-proteins that selectively bind to natural l-proteins have gained significant biotechnological interest. However, the underlying structural principles governing such heterochiral protein–protein interactions remain largely unknown. In this study, we present the de novo design of d-proteins consisting of 50–65 residues, aiming to target specific surface regions of l-proteins or l-peptides. Our designer d-protein binders exhibit nanomolar affinity toward an artificial l-peptide, as well as two naturally occurring proteins of therapeutic significance: the D5 domain of human tropomyosin receptor kinase A (TrkA) and human interleukin-6 (IL-6). Notably, these d-protein binders demonstrate high enantiomeric specificity and target specificity. In cell-based experiments, designer d-protein binders effectively inhibited the downstream signaling of TrkA and IL-6 with high potency. Moreover, these binders exhibited remarkable thermal stability and resistance to protease degradation. Crystal structure of the designed heterochiral d-protein–l-peptide complex, obtained at a resolution of 2.0 Å, closely resembled the design model, indicating that the computational method employed is highly accurate. Furthermore, the crystal structure provides valuable information regarding the interactions between helical l-peptides and d-proteins, particularly elucidating a novel mode of heterochiral helix–helix interactions. Leveraging the design of d-proteins specifically targeting l-peptides or l-proteins opens up avenues for systematic exploration of the mirror-image protein universe, paving the way for a diverse range of applications.

Styles APA, Harvard, Vancouver, ISO, etc.

16

Weh, Manuel, Kazutaka Shoyama et Frank Würthner. « Preferential molecular recognition of heterochiral guests within a cyclophane receptor ». Nature Communications 14, n^o 1 (16 janvier 2023). http://dx.doi.org/10.1038/s41467-023-35851-3.

Texte intégral

Résumé :

AbstractThe discrimination of enantiomers by natural receptors is a well-established phenomenon. In contrast the number of synthetic receptors with the capability for enantioselective molecular recognition of chiral substrates is scarce and for chiral cyclophanes indicative for a preferential binding of homochiral guests. Here we introduce a cyclophane composed of two homochiral core-twisted perylene bisimide (PBI) units connected by p-xylylene spacers and demonstrate its preference for the complexation of [5]helicene of opposite helicity compared to the PBI units of the host. The pronounced enantio-differentiation of this molecular receptor for heterochiral guests can be utilized for the enrichment of the P-PBI-M-helicene-P-PBI epimeric bimolecular complex. Our experimental results are supported by DFT calculations, which reveal that the sterically demanding bay substituents attached to the PBI chromophores disturb the helical shape match of the perylene core and homochiral substrates and thereby enforce the formation of syndiotactic host-guest complex structures. Hence, the most efficient substrate binding is observed for those aromatic guests, e. g. perylene, [4]helicene, phenanthrene and biphenyl, that can easily adapt in non-planar axially chiral conformations due to their inherent conformational flexibility. In all cases the induced chirality for the guest is opposed to those of the embedding PBI units, leading to heterochiral host-guest structures.

Styles APA, Harvard, Vancouver, ISO, etc.

17

Ghorai, Sandipan, et Ramalingam Natarajan. « Chiral Self‐Sorting, Spontaneous Resolution, and Hierarchical Self‐Assembly in Metal–Organic Cages ». Small, 6 mai 2024. http://dx.doi.org/10.1002/smll.202400842.

Texte intégral

Résumé :

AbstractThe ability to collectively program chiral recognition and the hierarchical self‐assembly of molecular and supramolecular building blocks into complex higher‐order superstructures is a significant goal in supramolecular chemistry. Metal–organic cages are excellent model systems to examine chiral self‐sorting and build hierarchical self‐assembly. Herein, details on how limiting the conformational flexibility and incorporating hydrogen bonding functional groups in the ligands can influence chiral self‐sorting and hierarchical self‐assembly of metal–organic cages are reported. The urea‐functionalized axially chiral bis‐pyridyl ligands afford high‐fidelity in chiral self‐sorting in Pd2L4 cages, when they have fewer conformations. Ligand L1, with more conformations, affords mixture of heterochiral and homochiral cages (≈70:30). Among them, the heterochiral cage adopts unusual twisted conformation and self‐assembles into 2D sheets, linked by anion coordination between urea and nitrate. Ligand L2, with fewer conformations, affords homochiral cages via high‐fidelity chiral self‐sorting. The choice of counter anions influences further self‐sorting in the solid state: racemate with PF6− and spontaneously resolves conglomerate with BF4−. Urea‐BF4 hydrogen bonding directs hierarchical self‐assembly of the Pd2L4 metal–organic cages into super‐cubic networks. The study introduces a new approach in hierarchical self‐assembly of metal–organic cages into higher‐order networks aided by hydrogen bonding anion coordination with functional ligands.

Styles APA, Harvard, Vancouver, ISO, etc.

18

el Battioui, Kamal, Sohini Chakraborty, András Wacha, Dániel Molnár, Mayra Quemé-Peña, Imola Cs Szigyártó, Csenge Lilla Szabó et al. « In situ captured antibacterial action of membrane-incising peptide lamellae ». Nature Communications 15, n^o 1 (23 avril 2024). http://dx.doi.org/10.1038/s41467-024-47708-4.

Texte intégral

Résumé :

AbstractDeveloping unique mechanisms of action are essential to combat the growing issue of antimicrobial resistance. Supramolecular assemblies combining the improved biostability of non-natural compounds with the complex membrane-attacking mechanisms of natural peptides are promising alternatives to conventional antibiotics. However, for such compounds the direct visual insight on antibacterial action is still lacking. Here we employ a design strategy focusing on an inducible assembly mechanism and utilized electron microscopy (EM) to follow the formation of supramolecular structures of lysine-rich heterochiral β3-peptides, termed lamellin-2K and lamellin-3K, triggered by bacterial cell surface lipopolysaccharides. Combined molecular dynamics simulations, EM and bacterial assays confirmed that the phosphate-induced conformational change on these lamellins led to the formation of striped lamellae capable of incising the cell envelope of Gram-negative bacteria thereby exerting antibacterial activity. Our findings also provide a mechanistic link for membrane-targeting agents depicting the antibiotic mechanism derived from the in-situ formation of active supramolecules.

Styles APA, Harvard, Vancouver, ISO, etc.

19

Kang, Xing, Li Wang, Bingyu Liu, Shuyi Zhou, Yingguo Li, Shuai-Liang Yang, Rui Yao et al. « Mechanically rigid metallopeptide nanostructures achieved by highly efficient folding ». Nature Synthesis, 5 septembre 2024. http://dx.doi.org/10.1038/s44160-024-00640-3.

Texte intégral

Résumé :

AbstractNatural proteins must fold into complex three-dimensional structures to achieve excellent mechanical properties vital for biological functions, but this has proven to be exceptionally difficult to control in synthetic systems. As such, the long-standing issue of low mechanical rigidity and stability induced by misfolding constrains the physical and chemical properties of self-assembling peptide materials. Here we introduce a mixed-chirality strategy that enhances folding efficiency in topologically interlocked metallopeptide nanostructures. The orderly entanglement of heterochiral peptide-derived linkers can fold into a compact three-dimensional catenane. These folding-mediated secondary structural changes not only generate biomimetic binding pockets derived from individual peptide strands but also result in strong chiral amplification by the tight interlocking manner. Notably, this strategic ‘chirality mutation’ alters their arrangement into tertiary structures and is pivotal in achieving exceptional mechanical rigidity observed in the metallopeptide crystals, which exhibit a Young’s modulus of 157.6 GPa, approximately tenfold higher than the most rigid proteinaceous materials in nature. This unusual nature is reflected in enhanced peptide-binding properties and heightened antimicrobial activities relative to its unfolded counterpart.

Styles APA, Harvard, Vancouver, ISO, etc.

20

Domingos, Sérgio R., Denis S. Tikhonov, Amanda L. Steber, Patrick Eschenbach, Sebastien Gruet, Helgi R. Hrodmarsson, Kévin Martin et al. « Evolution of the ionisation energy with the stepwise growth of chiral clusters of [4]helicene ». Nature Communications 15, n^o 1 (10 juin 2024). http://dx.doi.org/10.1038/s41467-024-48778-0.

Texte intégral

Résumé :

AbstractPolycyclic aromatic hydrocarbons (PAHs) are widely established as ubiquitous in the interstellar medium (ISM), but considering their prevalence in harsh vacuum environments, the role of ionisation in the formation of PAH clusters is poorly understood, particularly if a chirality-dependent aggregation route is considered. Here we report on photoelectron spectroscopy experiments on [4]helicene clusters performed with a vacuum ultraviolet synchrotron beamline. Aggregates (up to the heptamer) of [4]helicene, the smallest PAH with helical chirality, were produced and investigated with a combined experimental and theoretical approach using several state-of-the-art quantum-chemical methodologies. The ionisation onsets are extracted for each cluster size from the mass-selected photoelectron spectra and compared with calculations of vertical ionisation energies. We explore the complex aggregation topologies emerging from the multitude of isomers formed through clustering of P and M, the two enantiomers of [4]helicene. The very satisfactory benchmarking between experimental ionisation onsets vs. predicted ionisation energies allows the identification of theoretically predicted potential aggregation motifs and corresponding energetic ordering of chiral clusters. Our structural models suggest that a homochiral aggregation route is energetically favoured over heterochiral arrangements with increasing cluster size, hinting at potential symmetry breaking in PAH cluster formation at the scale of small grains.

Styles APA, Harvard, Vancouver, ISO, etc.

21

Seo, Wonbin, Carter S. Haines, Hongdeok Kim, Chae‐Lin Park, Shi Hyeong Kim, Sungmin Park, Dong‐Gyun Kim et al. « Azobenzene‐Functionalized Semicrystalline Liquid Crystal Elastomer Springs for Underwater Soft Robotic Actuators ». Small, 21 octobre 2024. http://dx.doi.org/10.1002/smll.202406493.

Texte intégral

Résumé :

AbstractAs actuated devices become smaller and more complex, there is a need for smart materials and structures that directly function as complete mechanical units without an external power supply. The strategy uses light‐powered, twisted, and coiled azobenzene‐functionalized semicrystalline liquid crystal elastomer (AC‐LCE) springs. This twisting and coiling, which has previously been used for only thermally, electrochemically, or absorption‐powered muscles, maximizes uniaxial and radial actuation. The specially designed photochemical muscles can undergo about 60% tensile stroke and provide 15 kJ m−3 of work capacity in response to light, thus providing about three times and two times higher performance, respectively, than previous azobenzene actuators. Since this actuation is photochemical, driven by ultraviolet (UV) light and reversed by visible light, isothermal actuation can occur in a range of environmental conditions, including underwater. In addition, photoisomerization of the AC‐LCEs enables unique latch‐like actuation, eliminating the need for continuous energy application to maintain the stroke. Also, as the light‐powered muscles processed to be either homochiral or heterochiral, the direction of actuation can be reversed. The presented approach highlights the novel capabilities of photochemical actuator materials that can be manipulated in untethered, isothermal, and wet environmental conditions, thus suggesting various potential applications, including underwater soft robotics.

Styles APA, Harvard, Vancouver, ISO, etc.

Articles de revues sur le sujet « Heterochiral complex »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres