Articoli di riviste: "Sigma-Hole interactions"

1

Lim, Jason Y. C., e Paul D. Beer. "Sigma-Hole Interactions in Anion Recognition". Chem 4, n. 4 (aprile 2018): 731–83. http://dx.doi.org/10.1016/j.chempr.2018.02.022.

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Pinheiro, Pedro de Sena Murteira, Daniel Alencar Rodrigues, Marina Amaral Alves, Luzineide Wanderley Tinoco, Glaucio Braga Ferreira, Carlos Mauricio Rabello de Sant’Anna e Carlos Alberto Manssour Fraga. "Theoretical and experimental characterization of 1,4-N⋯S σ-hole intramolecular interactions in bioactive N-acylhydrazone derivatives". New Journal of Chemistry 42, n. 1 (2018): 497–505. http://dx.doi.org/10.1039/c7nj03543h.

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Aakeröy, Christer B., Saman Alavi, Lee Brammer, David L. Bryce, Timothy Clark, Janet E. Del Bene, Alison J. Edwards et al. "Computational approaches and sigma-hole interactions: general discussion". Faraday Discussions 203 (2017): 131–63. http://dx.doi.org/10.1039/c7fd90061a.

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Quiñonero, D. "Sigma-hole carbon-bonding interactions in carbon–carbon double bonds: an unnoticed contact". Physical Chemistry Chemical Physics 19, n. 23 (2017): 15530–40. http://dx.doi.org/10.1039/c7cp01780d.

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Hendinejad, Niloufar, e Qadir K. Timerghazin. "Biological control of S-nitrosothiol reactivity: potential role of sigma-hole interactions". Physical Chemistry Chemical Physics 22, n. 12 (2020): 6595–605. http://dx.doi.org/10.1039/c9cp06377c.

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S-Nitrosothiols, ubiquitous biological derivatives of nitric oxide, can engage in σ-hole/bonding with Lewis bases, which, in combination with hydrogen bonding with Lewis acids, could be the basis of enzymatic control of S-nitrosothiol reactions.

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Weinhold, Frank. "Anti-Electrostatic Pi-Hole Bonding: How Covalency Conquers Coulombics". Molecules 27, n. 2 (7 gennaio 2022): 377. http://dx.doi.org/10.3390/molecules27020377.

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Intermolecular bonding attraction at π-bonded centers is often described as “electrostatically driven” and given quasi-classical rationalization in terms of a “pi hole” depletion region in the electrostatic potential. However, we demonstrate here that such bonding attraction also occurs between closed-shell ions of like charge, thereby yielding locally stable complexes that sharply violate classical electrostatic expectations. Standard DFT and MP2 computational methods are employed to investigate complexation of simple pi-bonded diatomic anions (BO−, CN−) with simple atomic anions (H−, F−) or with one another. Such “anti-electrostatic” anion–anion attractions are shown to lead to robust metastable binding wells (ranging up to 20–30 kcal/mol at DFT level, or still deeper at dynamically correlated MP2 level) that are shielded by broad predissociation barriers (ranging up to 1.5 Å width) from long-range ionic dissociation. Like-charge attraction at pi-centers thereby provides additional evidence for the dominance of 3-center/4-electron (3c/4e) nD-π*AX interactions that are fully analogous to the nD-σ*AH interactions of H-bonding. Using standard keyword options of natural bond orbital (NBO) analysis, we demonstrate that both n-σ* (sigma hole) and n-π* (pi hole) interactions represent simple variants of the essential resonance-type donor-acceptor (Bürgi–Dunitz-type) attraction that apparently underlies all intermolecular association phenomena of chemical interest. We further demonstrate that “deletion” of such π*-based donor-acceptor interaction obliterates the characteristic Bürgi–Dunitz signatures of pi-hole interactions, thereby establishing the unique cause/effect relationship to short-range covalency (“charge transfer”) rather than envisioned Coulombic properties of unperturbed monomers.

7

Lee, Jiwon, Lucia Myongwon Lee, Zachary Arnott, Hilary Jenkins, James F. Britten e Ignacio Vargas-Baca. "Sigma-hole interactions in the molecular and crystal structures of N-boryl benzo-2,1,3-selenadiazoles". New Journal of Chemistry 42, n. 13 (2018): 10555–62. http://dx.doi.org/10.1039/c8nj00553b.

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Jiao, Yinchun, e Frank Weinhold. "What Is the Nature of Supramolecular Bonding? Comprehensive NBO/NRT Picture of Halogen and Pnicogen Bonding in RPH2···IF/FI Complexes (R = CH3, OH, CF3, CN, NO2)". Molecules 24, n. 11 (31 maggio 2019): 2090. http://dx.doi.org/10.3390/molecules24112090.

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We employ a variety of natural bond orbital (NBO) and natural resonance theory (NRT) tools to comprehensively investigate the nature of halogen and pnicogen bonding interactions in RPH2···IF/FI binary complexes (R = CH3, OH, CF3, CN, and NO2) and the tuning effects of R-substituents. Though such interactions are commonly attributed to “sigma-hole”-type electrostatic effects, we show that they exhibit profound similarities and analogies to the resonance-type 3-center, 4-electron (3c/4e) donor-acceptor interactions of hydrogen bonding, where classical-type “electrostatics” are known to play only a secondary modulating role. The general 3c/4e resonance perspective corresponds to a continuous range of interatomic A···B bond orders (bAB), spanning both the stronger “covalent” interactions of the molecular domain (say, bAB ≥ ½) and the weaker interactions (bAB ˂ ½, often misleadingly termed “noncovalent”) that underlie supramolecular complexation phenomena. We show how a unified NBO/NRT-based description of hydrogen, halogen, pnicogen, and related bonding yields an improved predictive utility and intuitive understanding of empirical trends in binding energies, structural geometry, and other measurable properties that are expected to be manifested in all such supramolecular interaction phenomena.

9

Zierkiewicz, Wiktor, Mariusz Michalczyk e Steve Scheiner. "Noncovalent Bonds through Sigma and Pi-Hole Located on the Same Molecule. Guiding Principles and Comparisons". Molecules 26, n. 6 (20 marzo 2021): 1740. http://dx.doi.org/10.3390/molecules26061740.

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Over the last years, scientific interest in noncovalent interactions based on the presence of electron-depleted regions called σ-holes or π-holes has markedly accelerated. Their high directionality and strength, comparable to hydrogen bonds, has been documented in many fields of modern chemistry. The current review gathers and digests recent results concerning these bonds, with a focus on those systems where both σ and π-holes are present on the same molecule. The underlying principles guiding the bonding in both sorts of interactions are discussed, and the trends that emerge from recent work offer a guide as to how one might design systems that allow multiple noncovalent bonds to occur simultaneously, or that prefer one bond type over another.

10

Thomas, Sajesh P., Amol G. Dikundwar, Sounak Sarkar, Mysore S. Pavan, Rumpa Pal, Venkatesha R. Hathwar e Tayur N. Guru Row. "The Relevance of Experimental Charge Density Analysis in Unraveling Noncovalent Interactions in Molecular Crystals". Molecules 27, n. 12 (8 giugno 2022): 3690. http://dx.doi.org/10.3390/molecules27123690.

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The work carried out by our research group over the last couple of decades in the context of quantitative crystal engineering involves the analysis of intermolecular interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding using experimental charge density methodology is reviewed. The focus is to extract electron density distribution in the intermolecular space and to obtain guidelines to evaluate the strength and directionality of such interactions towards the design of molecular crystals with desired properties. Following the early studies on halogen bonding interactions, several “sigma-hole” interaction types with similar electrostatic origins have been explored in recent times for their strength, origin, and structural consequences. These include interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding. Experimental X-ray charge density analysis has proved to be a powerful tool in unraveling the strength and electronic origin of such interactions, providing insights beyond the theoretical estimates from gas-phase molecular dimer calculations. In this mini-review, we outline some selected contributions from the X-ray charge density studies to the field of non-covalent interactions (NCIs) involving elements of the groups 14–17 of the periodic table. Quantitative insights into the nature of these interactions obtained from the experimental electron density distribution and subsequent topological analysis by the quantum theory of atoms in molecules (QTAIM) have been discussed. A few notable examples of weak interactions have been presented in terms of their experimental charge density features. These examples reveal not only the strength and beauty of X-ray charge density multipole modeling as an advanced structural chemistry tool but also its utility in providing experimental benchmarks for the theoretical studies of weak interactions in crystals.

11

Arjmand, Farukh, Salman khursheed, Thierry Roisnel e Hifzur R. Siddique. "Copper (II)-based halogen-substituted chromone antitumor drug entities: Studying biomolecular interactions with ct-DNA mediated by sigma hole formation and cytotoxicity activity". Bioorganic Chemistry 104 (novembre 2020): 104327. http://dx.doi.org/10.1016/j.bioorg.2020.104327.

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Michalczyk, Zierkiewicz, Wysokiński e Scheiner. "Theoretical Studies of IR and NMR Spectral Changes Induced by Sigma-Hole Hydrogen, Halogen, Chalcogen, Pnicogen, and Tetrel Bonds in a Model Protein Environment". Molecules 24, n. 18 (12 settembre 2019): 3329. http://dx.doi.org/10.3390/molecules24183329.

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Various types of σ-hole bond complexes were formed with FX, HFY, H2FZ, and H3FT (X = Cl, Br, I; Y = S, Se, Te; Z = P, As, Sb; T = Si, Ge, Sn) as Lewis acid. In order to examine their interactions with a protein, N-methylacetamide (NMA), a model of the peptide linkage was used as the base. These noncovalent bonds were compared by computational means with H-bonds formed by NMA with XH molecules (X = F, Cl, Br, I). In all cases, the A–F bond, which lies opposite the base and is responsible for the σ-hole on the A atom (A refers to the bridging atom), elongates and its stretching frequency undergoes a shift to the red with a band intensification, much as what occurs for the X–H bond in a H-bond (HB). Unlike the NMR shielding decrease seen in the bridging proton of a H-bond, the shielding of the bridging A atom is increased. The spectroscopic changes within NMA are similar for H-bonds and the other noncovalent bonds. The C=O bond of the amide is lengthened and its stretching frequency red-shifted and intensified. The amide II band shifts to higher frequency and undergoes a small band weakening. The NMR shielding of the O atom directly involved in the bond rises, whereas the C and N atoms both undergo a shielding decrease. The frequency shifts of the amide I and II bands of the base as well as the shielding changes of the three pertinent NMA atoms correlate well with the strength of the noncovalent bond.

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Radha, Anu, Sandeep Kumar, Deepika Sharma, Amanpreet K. Jassal, Jan K. Zaręba, Antonio Franconetti, Antonio Frontera, Puneet Sood e Sushil K. Pandey. "Indirect influence of alkyl substituent on sigma-hole interactions: The case study of antimony(III) diphenyldithiophosphates with covalent Sb-S and non-covalent Sb⋯S pnictogen bonds". Polyhedron 173 (novembre 2019): 114126. http://dx.doi.org/10.1016/j.poly.2019.114126.

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14

Elakkat, Vijayanath, Chu-Chun Chang, Jun-Yu Chen, Yung-Cheng Fang, Chia-Rui Shen, Ling-Kung Liu e Norman Lu. "Correction: The first two examples of halogen bonding with a sigma hole-donating fluorine in the Csp3–F⋯Osp3 interaction from polyfluorinated trans-dihalo-palladium(ii) di-substituted pyridine complexes". Chemical Communications 55, n. 99 (2019): 15004. http://dx.doi.org/10.1039/c9cc90530h.

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Correction for ‘The first two examples of halogen bonding with a sigma hole-donating fluorine in the C_sp³–F⋯O_sp³ interaction from polyfluorinated trans-dihalo-palladium(ii) di-substituted pyridine complexes’ by Vijayanath Elakkat et al., Chem. Commun., 2019, DOI: 10.1039/c9cc06731k.

15

St-Gallay, Stephen A., Neil Bennett, Susan E. Critchlow, Nicola Curtis, Gareth Davies, Judit Debreczeni, Nicola Evans et al. "A High-Throughput Screening Triage Workflow to Authenticate a Novel Series of PFKFB3 Inhibitors". SLAS DISCOVERY: Advancing the Science of Drug Discovery 23, n. 1 (25 settembre 2017): 11–22. http://dx.doi.org/10.1177/2472555217732289.

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A high-throughput screen (HTS) of human 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) resulted in several series of compounds with the potential for further optimization. Informatics was used to identify active chemotypes with lead-like profiles and remove compounds that commonly occurred as actives in other HTS screens. The activities were confirmed with IC50 measurements from two orthogonal assay technologies, and further analysis of the Hill slopes and comparison of the ratio of IC50 values at 10 times the enzyme concentration were used to identify artifact compounds. Several series of compounds were rejected as they had both high slopes and poor ratios. A small number of compounds representing the different leading series were assessed using isothermal titration calorimetry, and the X-ray crystal structure of the complex with PFKFB3 was solved. The orthogonal assay technology and isothermal calorimetry were demonstrated to be unreliable in identifying false-positive compounds in this case. Presented here is the discovery of the dihydropyrrolopyrimidinone series of compounds as active and novel inhibitors of PFKFB3, shown by X-ray crystallography to bind to the adenosine triphosphate site. The crystal structures of this series also reveal it is possible to flip the binding mode of the compounds, and the alternative orientation can be driven by a sigma-hole interaction between an aromatic chlorine atom and a backbone carbonyl oxygen. These novel inhibitors will enable studies to explore the role of PFKFB3 in driving the glycolytic phenotype of tumors.

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Elakkat, Vijayanath, Chu-Chun Chang, Jun-Yu Chen, Yung-Cheng Fang, Chia-Rui Shen, Ling-Kung Liu e Norman Lu. "The first two examples of halogen bonding with a sigma hole-donating fluorine in the Csp3–F⋯Osp3 interaction from polyfluorinated trans-dihalo-palladium(ii) di-substituted pyridine complexes". Chemical Communications 55, n. 95 (2019): 14259–62. http://dx.doi.org/10.1039/c9cc06731k.

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Molecular packing diagram of trans-[PdCl₂(3-HCF₂CF₂CH₂OCH₂py)₂] (left) showing a C8–F2⋯O1 halogen bond; (right) its stacking piles showing a herringbone pattern.

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Becerra González, J., J. A. Acosta-Pulido e R. Clavero. "Optical spectral characterization of the TeV extreme blazar 2WHSP J073326.7+515354". Monthly Notices of the Royal Astronomical Society 494, n. 4 (28 aprile 2020): 6036–42. http://dx.doi.org/10.1093/mnras/staa1144.

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ABSTRACT The emission from the relativistic jets in blazars usually outshines their host galaxies, challenging the determination of their distances and the characterization of the stellar population. The situation becomes more favourable in the case of the extreme blazars (EHBLs), for which the bulk of the emission of the relativistic jets is emitted at higher energies, unveiling the optical emission from the host galaxy. The distance determination is fundamental for the study of the intrinsic characteristics of the blazars, especially to estimate the intrinsic gamma-ray spectra distorted due to the interaction with the extragalactic background light. In this work, we report on the properties of 2WHSP J073326.7+515354 host galaxy in the optical band, which is one of the few EHBLs detected at TeV energies. We present the first measurement of the distance of the source, z = 0.065 04 ± 0.000 02 (velocity dispersion $\sigma =237 \pm 9\, \mathrm{km s^{-1}}$). We also perform a detailed study of the stellar population of its host galaxy. We find that the mass-weighted mean stellar age is $11.72\pm 0.06\, \mathrm{Gyr}$ and the mean metallicity [M/H] = 0.159 ± 0.016. In addition, a morphological study of the host galaxy is also carried out. The surface brightness distribution is modelled by a composition of a dominant classical bulge (Re = 3.77 ± 1 arcsec or equivalently 4.74 kpc) plus an unresolved source which corresponds to the active nucleus. The black hole mass is estimated using both the mass relation with the velocity dispersion and the absolute magnitude from the bulge yielding comparable results: $(4.8\pm 0.9)\times 10^8$ and $(3.7\pm 1.0)\times 10^8\, \mathrm{ M}_{\odot }$, respectively.

18

Andriollo, Paolo, George Procopiou, Daniella M. di Mascio, Paul J. Jackson, Khondaker M. Rahman, Keith R. Fox e David E. Thurston. "Abstract 1750: Design and development of a novel highly sequence-selective guanine mono-alkylating DNA-interactive ADC payload suitable for solid tumor treatments". Cancer Research 82, n. 12_Supplement (15 giugno 2022): 1750. http://dx.doi.org/10.1158/1538-7445.am2022-1750.

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Abstract Antibody-Drug Conjugates (ADCs) are a fast-growing class of targeted cancer therapeutic agents with over ten approved and greater than 100 in various stages of clinical development. The pyridinobenzodiazepines (PDDs) are a new class of DNA-interactive sequence-selective Guanine mono-alkylating ADC payloads which contain a sequence recognition component with sufficient span to guide them to specific DNA sequences (e.g., transcription factor binding sites). A high potency PDD, FGX15-147, has been developed that contains a bi-aryl moiety capable of forming an intramolecular ‘sigma-hole’ interaction with DNA bases, thus providing the molecule with a unique sequence-selectivity profile when compared to other DNA-interactive agents. DNA footprinting data will be presented indicating that the molecule, which spans 8-9 DNA base pairs in the minor groove, has an increased sequence selectivity compared with related analogues, preferring DNA regions containing two guanines 2-4 base pairs apart. FGX15-147 is highly cytotoxic in vitro (e.g., IC50 = 0.30 nM in SW60; 1.6 nM in LIM1215 and 0.142 nM in SW48, after 96 hours incubation), and is thought to exert its activity through a combination of DNA alkylation and inhibiting the binding of important oncogenic transcription factors such as Hypoxia Inducible Factor (HIF) to DNA (demonstrated through an in vitro Transcription Factor Array assay). HIF is known to be involved in the development of a large number of solid malignancies, including pancreatic cancer. To explore the utility of FGX15-147 as an ADC payload, it was conjugated to trastuzumab in a stochastic manner (DAR 1.6) using a Maleimide-Valine-Alanine linker construct. The resulting ADC exhibited significant in vivo efficacy in a low copy number HER2+ pancreatic cancer Human Tumor Xenograft model using BALB-c mice transplanted with the CAPAN-1 cell line. Complete tumor regression was observed out to 60 days after a single dose of 2 mg/kg comparing favorably to a 10 mg/kg dose of trastuzumab deruxtecan (Enhertu®) in the same study in which substantial tumor regrowth had occurred by 57 days. In a standard mouse model, the FGX15-147-based ADC had a good tolerability profile with a Maximum Tolerated Dose (MTD) of at least 16 mg/kg. Overall, the favorable tolerability and efficacy profile of FGX15-147 in an ADC format suggests that it represents a potentially valuable approach for the treatment of solid tumors. Citation Format: Paolo Andriollo, George Procopiou, Daniella M. di Mascio, Paul J. Jackson, Khondaker M. Rahman, Keith R. Fox, David E. Thurston. Design and development of a novel highly sequence-selective guanine mono-alkylating DNA-interactive ADC payload suitable for solid tumor treatments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1750.

19

Docker, Andrew, e Matthew J. Langton. "Transmembrane anion transport mediated by sigma-hole interactions". Trends in Chemistry, giugno 2023. http://dx.doi.org/10.1016/j.trechm.2023.06.001.

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20

Hein, Robert, e Paul D. Beer. "Halogen Bonding and Chalcogen Bonding Mediated Sensing". Chemical Science, 2022. http://dx.doi.org/10.1039/d2sc01800d.

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Sigma-hole interactions, in particular halogen bonding (XB) and chalcogen bonding (ChB), have become indispensible tools in supramolecular chemistry, with wide-ranging applications in crystal engineering, catalysis and materials chemistry as well...

21

Pantig, Reggie C., e Ali Övgün. "Imprints of a gravitational wave through the weak field deflection of photons". Chinese Physics C, 21 maggio 2024. http://dx.doi.org/10.1088/1674-1137/ad4e25.

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Abstract This paper investigates the novel phenomenon of gravitational lensing experienced by gravitational waves traveling past a Schwarzschild black hole perturbed by a specific, first-order, polar gravitational wave. We utilize the Gauss-Bonnet theorem, uncovering a topological contribution to the deflection of light rays passing near the black hole. We demonstrate that the deflection angle can be determined by analyzing a region entirely outside the light ray's path, leading to a calculation based solely on the parameters of the perturbing wave (Legendre polynomial order, $l$, and frequency, $\sigma$). This approach offers a unique perspective on gravitational lensing and expands our understanding of black hole interactions with gravitational waves.

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Ibrahim, Mahmoud A. A., Rehab R. A. Saeed, Mohammed N. I. Shehata, Nayra A. M. Moussa, Ahmed M. Tawfeek, Muhammad Naeem Ahmed, Mohamed K. Abd El-Rahman e Tamer Shoeib. "Sigma-Hole and Lone-Pair-Hole Site-Based Interactions of Seesaw Tetravalent Chalcogen-Bearing Molecules with Lewis Bases". ACS Omega, 30 agosto 2023. http://dx.doi.org/10.1021/acsomega.3c03981.

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23

Schwartz, Mathieu, Valentin Boichot, Mariam Muradova, Pablo Fournier, Patrick Senet, Adrien Nicolai, Francis Canon et al. "Structure–activity analysis suggests an olfactory function for the unique antennal delta glutathione transferase of Apis mellifera". FEBS Letters, 7 novembre 2023. http://dx.doi.org/10.1002/1873-3468.14770.

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Glutathione transferases (GST) are detoxification enzymes that conjugate glutathione to a wide array of molecules. In the honey bee Apis mellifera, AmGSTD1 is the sole member of the delta class of GSTs, with expression in antennae. Here, we structurally and biochemically characterized AmGSTD1 to elucidate its function. We showed that AmGSTD1 can efficiently catalyse the glutathione conjugation of classical GST substrates. Additionally, AmGSTD1 exhibits binding properties with a range of odorant compounds. AmGSTD1 has a peculiar interface with a structural motif we propose to call ‘sulfur sandwich’. This motif consists of a cysteine disulfide bridge sandwiched between the sulfur atoms of two methionine residues and is stabilized by CH…S hydrogen bonds and S…S sigma‐hole interactions. Thermal stability studies confirmed that this motif is important for AmGSTD1 stability and, thus, could facilitate its functions in olfaction.

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Nandi, Goutam, Rohith Phaneendra Bandaru, Ranjan Patra, Ananda Kumar Jami e Bharat Kumar Tripuramallu. "Impact of Electron-Withdrawing Effect on Sigma Hole Via Bromine-Based Interactions in Zn-5,10,15,20-tetra(4-bromo-2,6-difluoro Phenyl) Porphyrin". Crystal Growth & Design, 10 luglio 2023. http://dx.doi.org/10.1021/acs.cgd.3c00543.

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Tay, Hui Min, Toby Johnson, Andrew Docker, Matthew Langton e Paul D. Beer. "Exploiting the Catenane Mechanical Bond Effect for Selective Halide Anion Transmembrane Transport". Angewandte Chemie International Edition, 29 settembre 2023. http://dx.doi.org/10.1002/anie.202312745.

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The first examples of [2]catenanes capable of selective anion transport across a lipid bilayer are reported. The neutral halogen bonding (XB) [2]catenanes were prepared via a chloride template‐directed strategy in an unprecedented demonstration of using XB∙∙∙anion interactions to direct catenane assembly from all‐neutral components. Anion binding experiments in aqueous‐organic solvent media revealed strong halide over oxoanion selectivity, and a marked enhancement in the chloride and bromide affinities of the catenanes relative to their constituent macrocycles. The catenanes displayed an anti‐Hofmeister binding preference for bromide over the larger iodide anion, illustrating the efficacy of employing sigma‐hole interactions in conjunction with the mechanical bond effect to tune receptor selectivity. Transmembrane anion transport studies conducted in POPC LUVs revealed that the catenanes were more effective anion transporters than the constituent macrocycles, with high chloride over hydroxide selectivity, which is critical to potential therapeutic applications of anionophores. Remarkably these outperform existing acyclic halogen bonding anionophores with regards to this selectivity. Record chloride over nitrate anion transport selectivity was also observed. This represents a rare example of the direct translation of intrinsic anion binding affinities to anion transport behaviour, and demonstrates the key role of the catenane mechanical bond effect for enhanced anion transport selectivity.

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Tay, Hui Min, Toby Johnson, Andrew Docker, Matthew Langton e Paul D. Beer. "Exploiting the Catenane Mechanical Bond Effect for Selective Halide Anion Transmembrane Transport". Angewandte Chemie, 29 settembre 2023. http://dx.doi.org/10.1002/ange.202312745.

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The first examples of [2]catenanes capable of selective anion transport across a lipid bilayer are reported. The neutral halogen bonding (XB) [2]catenanes were prepared via a chloride template‐directed strategy in an unprecedented demonstration of using XB∙∙∙anion interactions to direct catenane assembly from all‐neutral components. Anion binding experiments in aqueous‐organic solvent media revealed strong halide over oxoanion selectivity, and a marked enhancement in the chloride and bromide affinities of the catenanes relative to their constituent macrocycles. The catenanes displayed an anti‐Hofmeister binding preference for bromide over the larger iodide anion, illustrating the efficacy of employing sigma‐hole interactions in conjunction with the mechanical bond effect to tune receptor selectivity. Transmembrane anion transport studies conducted in POPC LUVs revealed that the catenanes were more effective anion transporters than the constituent macrocycles, with high chloride over hydroxide selectivity, which is critical to potential therapeutic applications of anionophores. Remarkably these outperform existing acyclic halogen bonding anionophores with regards to this selectivity. Record chloride over nitrate anion transport selectivity was also observed. This represents a rare example of the direct translation of intrinsic anion binding affinities to anion transport behaviour, and demonstrates the key role of the catenane mechanical bond effect for enhanced anion transport selectivity.

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Balthazar, Bruno, Amit Giveon, David Kutasov e Emil J. Martinec. "Asymptotically free AdS3/CFT2". Journal of High Energy Physics 2022, n. 1 (gennaio 2022). http://dx.doi.org/10.1007/jhep01(2022)008.

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Abstract We propose a new AdS3/CFT2 duality, in which the bulk string theory has a target spacetime AdS3 times a squashed three-sphere $$ {\mathbbm{S}}_{\flat}^3 $$ S ♭ 3 , and the dual CFT2 is a symmetric product of sigma models on ℝϕ×$$ {\mathbbm{S}}_{\flat}^3 $$ S ♭ 3 , deformed by a ϕ-dependent ℤ2 twist operator. The duality maps the asymptotic region of AdS3 to the region ϕ → ∞, where the twist interaction in the CFT2 turns off. The AdS3 backgrounds in question have RAdS< ℓs, and so lie on the string side of the string/black hole correspondence transition. As a consequence, the high energy density of states consists of a string gas in AdS3 rather than an ensemble of BTZ black holes. This property allows us to derive the dual CFT2 by a systematic analysis of the worldsheet string theory on AdS3.

Articoli di riviste sul tema "Sigma-Hole interactions"

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