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1.
Org Lett ; 22(1): 204-208, 2020 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-31846336

RESUMO

This study confirms the hypothesis that bambusurils (BUs) with equatorial sulfur atoms cannot assume an anion-binding jigger conformation due to strong intramolecular van der Waals attractive interactions. NMR, X-ray crystallography, and computation with newly synthesized eq-semithio-BU[4] and ax-semiaza-eq-semithio-BU[4]s indicate that they all assume compact conformations. Intramolecular distances and a torsional angle serve as reliable indicators of the conformation of any BU. Chemoselective alkylation at the peripheral (equatorial) thiourea functions provides a convenient entry to novel hetero-BUs.

2.
Nat Commun ; 10(1): 3443, 2019 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-31371724

RESUMO

Self-assembly of twelve pentatopic tectons, which have complementary edges or can be linked using either digonal or trigonal connectors, represents the optimal synthetic strategy to achieve spherical objects, such as chemical capsids. This process requires conditions that secure uninterrupted equilibria of binding and self-correction en route to the global energy minimum. Here we report the synthesis of a highly soluble, deca-heterosubstituted corannulene that bears five terpyridine ligands. Spontaneous self-assembly of twelve such tectons with 30 cadmium(II) cations produces a giant icosahedral capsid as a thermodynamically stable single product in high yield. Nuclear magnetic resonance (NMR) methods, mass spectrometry analyses, small-angle X-ray scattering, transmission electron microscopy, and atomic force microscopy indicate that this spherical capsid has an external diameter of nearly 6 nm and shell thickness of 1 nm, in agreement with molecular modeling. NMR and liquid chromatography evidences imply that chiral self-sorting complexation generates a racemic mixture of homochiral capsids.


Assuntos
Proteínas do Capsídeo/metabolismo , Capsídeo/química , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Montagem de Vírus/fisiologia , Antraquinonas , Cádmio/metabolismo , Modelos Moleculares , Termodinâmica
3.
Chemistry ; 25(58): 13336-13343, 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31269313

RESUMO

Bambusurils (BUs) are known to be rigid cavitands that feature an extended, jigger-like conformation, and the BU[6]s strongly bind anions within their hydrophobic cavity. These features are not necessarily shared by the family of perthio-BUs. This study reveals that perthio-BUs assume a compact conformation and perthio-BU[6]s are poor anion binders, crystallizing as anion-free species from solutions containing halide salts. Computational studies show that the equatorial sulfur atoms compete against guest anions for binding with the glycoluril methine groups via strong van der Waals (vdW) attractive interactions. These competitive contacts not only account for the diminished anion-binding of perthio-BUs, but also explain their compact conformation. The semithio- and perthio-BU[4]s form linear coordination polymers with HgII in the solid-state regardless of their intrinsic molecular conformation. The strong involvement of sulfur atoms in intramolecular interactions differentiates the equatorial from the axial (peripheral) heteroatoms, thus offering chemoselective and regioselective transformations.

4.
Angew Chem Int Ed Engl ; 58(12): 3688, 2019 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-30740844

RESUMO

Joel Bernstein, former Barry and Carol Kaye Professor of Applied Science at Ben-Gurion University, passed away on January 2, 2019. His legacy to the scientific community is a body of work on organic solid-state chemistry, chemical crystallography, polymorphism, hydrogen bonding, graph sets, structure-property relations, organic conducting materials, and pharmaceuticals.

5.
Chemistry ; 24(57): 15319-15328, 2018 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-30058729

RESUMO

The stepwise evolution of curved multifarene structures from planar precursors is demonstrated, highlighting three architectural design elements: 1) employment of various aromatic units, 2) changing the hybridization of the linking atoms from sp2 to sp3 , and 3) rigidification of the system by the introduction of five-membered rings. Similar design elements have been employed to transform graphene sheets into curved carbon structures. Specifically, the stepwise synthetic evolution of multifarene[2+2], which has a curved, quite rigid structure, begins with a planar, tetraimine precursor, conversion to pairs of vicinal diamines, and the transformation of these pairs to cyclic thiourea groups. This process was probed by NMR spectroscopy and X-ray crystallography. Since varying the carbonylation conditions resulted in carbamates or thiocarbamates rather than the urea or thiourea isomers, the isomeric interconversion was studied both experimentally and by DFT computations. The carbamate versus urea preference was found to reflect either kinetic or thermodynamic control, respectively.

6.
Chem Commun (Camb) ; 53(54): 7557-7560, 2017 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-28634604

RESUMO

Semithiobambus[6]uril is shown to be an efficient transmembrane anion transporter. Although all bambusuril analogs (having either O, S or N atoms in their portals) are excellent anion binders, only the sulfur analog is also an effective anion transporter capable of polarizing lipid membranes through selective anion uniport. This notable divergence reflects significant differences in the lipophilic character of the bambusuril analogs.


Assuntos
Imidazóis/metabolismo , Compostos Macrocíclicos/metabolismo , Ânions/química , Ânions/metabolismo , Transporte Biológico , Cloretos/química , Cloretos/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Imidazóis/química , Bicamadas Lipídicas/química , Bicamadas Lipídicas/metabolismo , Compostos Macrocíclicos/química , Estrutura Molecular
7.
J Am Chem Soc ; 139(24): 8138-8145, 2017 06 21.
Artigo em Inglês | MEDLINE | ID: mdl-28532152

RESUMO

In this paper, we report on the noteworthy attractive interaction between organic azides and the portal carbonyls of cucurbiturils. Five homologous bis-α,ω-azidoethylammonium alkanes were prepared, where the number of methylene groups between the ammonium groups ranges from 4 to 8. Their interactions with cucurbit[6]uril were studied by NMR spectroscopy, IR spectroscopy, X-ray crystallography, and computational methods. Remarkably, while the distance between the portal plane and most atoms at the guest end groups increases progressively with the molecular size, the ß-nitrogen atoms maintain a constant distance from the portal plane in all homologues, pointing at a strong attractive interaction between the azide group and the portal. Both crystallography and NMR support a specific electrostatic interaction between the carbonyl and the azide ß-nitrogen, which stabilizes the canonical resonance form with positive charge on the ß-nitrogen and negative charge on the γ-nitrogen. Quantum computational analyses strongly support electrostatics, in the form of orthogonal dipole-dipole interaction, as the main driver for this attraction. The alternative mechanism of n → π* orbital delocalization does not seem to play a significant role in this interaction. The computational studies also indicate that the interaction is not limited to azides, but generalizes to other isoelectronic heteroallene functions, such as isocyanate and isothiocyanate. This essentially unexploited attractive interaction could be more broadly utilized as a tool not only in relation to cucurbituril chemistry, but also for the design of novel supramolecular architectures.


Assuntos
Azidas/química , Compostos Macrocíclicos/química , Azidas/síntese química , Cristalografia por Raios X , Modelos Moleculares , Teoria Quântica
8.
Chemistry ; 22(26): 8848-54, 2016 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-27225332

RESUMO

Previous calculations of anion binding with various bambusuril analogs predicted that the replacement of oxygen by nitrogen atoms to produce semiaza-bambus[6]urils would award these new cavitands with multiple anion binding properties. This study validates the hypothesis by efficient synthesis, crystallography, thermogravimetric analysis and calorimetry. These unique host molecules are easily accessible from the corresponding semithio-bambusurils in a one-pot reaction, which converts a single anion receptor into a potential anion channel. Solid-state structures exhibit simultaneous accommodation of three anions, linearly positioned within the cavity along the main symmetry axis. The ability to hold anions at a short distance of about 4 Šis reminiscent of natural chloride channels in E. coli, which exhibit similar distances between their adjacent anion binding sites. The calculated transition-state energy for double-anion movement through the channel suggests that although these host-guest complexes are thermodynamically stable they enjoy high kinetic flexibility to render them efficient anion channels.


Assuntos
Compostos Aza/química , Imidazóis/química , Compostos Macrocíclicos/química , Alquinos/química , Ânions/química , Compostos Aza/metabolismo , Sítios de Ligação , Calorimetria , Canais de Cloreto/química , Canais de Cloreto/metabolismo , Cristalografia por Raios X , Análise Diferencial Térmica , Escherichia coli/metabolismo , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Éteres Cíclicos/química , Imidazóis/metabolismo , Cinética , Compostos Macrocíclicos/metabolismo , Conformação Molecular , Resorcinóis/química , Temperatura , Termodinâmica , Termogravimetria
9.
Phys Chem Chem Phys ; 18(19): 13180-5, 2016 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-26987849

RESUMO

This study was driven by the hypothesis that heteroatom replacement in bambusurils could significantly modify their anion binding properties. Indeed, calculations with various glycoluril and bambusuril analogs predict that such replacements significantly alter their molecular electrostatic potential and binding properties. Both polarization and electrostatic interactions contribute to anion binding, leading to a general trend of affinity among the neutral molecules: X = S > O > NH. In bambusurils the heteroatom replacement at the portal carbonyls affect the induced dipole more significantly than replacements at the equatorial carbonyls. The stronger polarization and stronger anion binding manifest the increased aptitude of the portal heteroatoms as electron sinks. Notably, this study predicts that protonated aza-bambusurils would not only bind multiple anions along their main axis, but could also function as synthetic anion channels.

10.
Chemistry ; 21(2): 536-40, 2015 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-25417852

RESUMO

Semithiobambusurils, which represent a new family of macrocyclic host molecules, have been prepared by a convenient, scalable synthesis. These new cavitands are double functional: they strongly bind a broad variety of anions in their interiors and metal ions at their sulfur-edged portals. The solid-state structure of semithiobambus[4]uril with HgCl2 demonstrates the ability of these compounds to form linear chains of coordination polymers with thiophillic metal ions. The crystal structure of semithiobambus[6]uril with tetraphenylphosphonium bromide exhibits the unique anion-binding properties of the host cavity and the characteristics of the binding site.

11.
Bioorg Med Chem Lett ; 25(2): 342-6, 2015 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-25499435

RESUMO

Our hypothesis that inflammation in asthma involves production of ozone by white blood cells and that ozone could be an inflammatory mediator suggests that scavengers of reactive oxygen species (ROS), for example, electron-rich olefins, could serve for prophylactic treatment of asthma. Olefins could provide chemical protection against either exogenous or endogenous ozone and other ROS. BALB/c mice pretreated by inhalation of d-limonene before an ovalbumin challenge exhibited significant attenuation of the allergic asthma symptoms. Diminution of the inflammatory process was evident by reduced levels of aldehydes, reduced counts of neutrophils in the BAL fluid and by histological tests. A surprising systemic effect was observed by decreased levels of aldehydes in the spleen, suggesting that the examination of tissues and organs that are remote from the inflammation foci could provide valuable information on the distribution of the oxidative stress and may serve as guide for targeted treatment.


Assuntos
Anti-Inflamatórios não Esteroides/farmacologia , Asma/tratamento farmacológico , Líquido da Lavagem Broncoalveolar/química , Cicloexenos/farmacologia , Inflamação/tratamento farmacológico , Ozônio/toxicidade , Espécies Reativas de Oxigênio/metabolismo , Terpenos/farmacologia , Administração por Inalação , Aldeídos/metabolismo , Animais , Anti-Inflamatórios não Esteroides/administração & dosagem , Asma/induzido quimicamente , Cicloexenos/administração & dosagem , Modelos Animais de Doenças , Inflamação/induzido quimicamente , Inflamação/metabolismo , Limoneno , Pulmão/efeitos dos fármacos , Pulmão/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Modelos Moleculares , Estrutura Molecular , Ovalbumina/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Baço/efeitos dos fármacos , Baço/metabolismo , Relação Estrutura-Atividade , Terpenos/administração & dosagem
12.
Chem Commun (Camb) ; 50(19): 2494-7, 2014 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-24457352

RESUMO

Multifarenes, a new class of macrocycles, which are constructed of alternating building blocks, are conveniently accessible by three complementary syntheses that provide modularity and scalability. In addition to metal-ion coordination, these cavitands show increased flexibility with increasing ring size, offering opportunities for induced fit to guest molecules.

13.
Stem Cells ; 31(11): 2396-407, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23922283

RESUMO

Increasing the number of ß cells is critical to a definitive therapy for diabetes. Previously, we discovered potent synthetic small molecule antagonists of the nuclear receptor transcription factor HNF4α. The natural ligands of HNF4α are thought to be fatty acids. Because obesity, in which there are high circulating levels of free fatty acids, is one of the few conditions leading to ß-cell hyperplasia, we tested the hypothesis that a potent HNF4α antagonist might stimulate ß-cell replication. A bioavailable HNF4α antagonist was injected into normal mice and rabbits and ß-cell ablated mice and the effect on ß-cell replication was measured. In normal mice and rabbits, the compound induced ß-cell replication and repressed the expression of multiple cyclin-dependent kinase inhibitors, including p16 that plays a critical role in suppressing ß-cell replication. Interestingly, in ß-cell ablated mice, the compound induced α- and δ-cell, in addition to ß-cell replication, and ß-cell number was substantially increased. Overall, the data presented here are consistent with a model in which the well-known effects of obesity and high fat diet on ß-cell replication occur by inhibition of HNF4α. The availability of a potent synthetic HNF4α antagonist raises the possibility that this effect might be a viable route to promote significant increases in ß-cell replication in diseases with reduced ß-cell mass, including type I and type II diabetes.


Assuntos
Fator 4 Nuclear de Hepatócito/antagonistas & inibidores , Células Secretoras de Insulina/metabolismo , Ácido Oleico/farmacologia , Ácidos Palmíticos/farmacologia , Animais , Processos de Crescimento Celular/efeitos dos fármacos , Diabetes Mellitus Experimental/tratamento farmacológico , Células Hep G2 , Humanos , Células Secretoras de Insulina/efeitos dos fármacos , Ilhotas Pancreáticas/efeitos dos fármacos , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos ICR , Coelhos , Distribuição Aleatória
14.
Chem Biol ; 20(5): 726-33, 2013 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-23706637

RESUMO

As computing devices, which process data and interconvert information, transducers can encode new information and use their output for subsequent computing, offering high computational power that may be equivalent to a universal Turing machine. We report on an experimental DNA-based molecular transducer that computes iteratively and produces biologically relevant outputs. As a proof of concept, the transducer accomplished division of numbers by 3. The iterative power was demonstrated by a recursive application on an obtained output. This device reads plasmids as input and processes the information according to a predetermined algorithm, which is represented by molecular software. The device writes new information on the plasmid using hardware that comprises DNA-manipulating enzymes. The computation produces dual output: a quotient, represented by newly encoded DNA, and a remainder, represented by E. coli phenotypes. This device algorithmically manipulates genetic codes.


Assuntos
Computadores Moleculares , Transdutores , Algoritmos , Sequência de Bases , DNA/genética , Escherichia coli/genética , Código Genético , Plasmídeos/genética
15.
Phys Chem Chem Phys ; 15(16): 6041-8, 2013 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-23493859

RESUMO

Our previously reported computational study of the decomposition pathways of triacetone triperoxide (TATP), 1, predicted that unlike most energetic materials, which involve self-combustion of fuel and oxidants, 1 decomposes via a thermoneutral, non-redox pathway that involves entropy burst. These predictions are now corroborated by time-resolved monitoring of deflagration or detonation of 1 using a fast video camera following initiation by a short pulse focused laser beam. While a fireball always accompanies the explosion of 1 under air, the formation of a fireball is totally prevented under a nitrogen atmosphere. These observations indicate that combustion of the gaseous primary products occurs as a secondary event only in the presence of exogenous oxygen. The composition of the product mixture was found to depend on the experimental conditions. With long pulse focused laser beam (150 µs at 1064 nm) at either 210 or 110 mJ, the small amounts of charcoal needed for initiation suggest that the energy required to initiate 1 by pulse laser is 4-10 mJ, much smaller than the energy required for initiation by either mechanical stress or electric discharge. This time-resolved study highlights the very unusual properties of the peroxide based explosives.


Assuntos
Compostos Heterocíclicos com 1 Anel/química , Lasers , Peróxidos/química , Cristalização , Entropia , Substâncias Explosivas/química , Fatores de Tempo
16.
Langmuir ; 29(7): 2217-23, 2013 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-23343474

RESUMO

Penta(tert-butylthio)corannulene and penta(4-dimethylaminophenylthio)corannulene form highly stable monolayers on gold surfaces, as indicated by X-ray photoelectron spectroscopy (XPS). Formation of these homogeneous monolayers involves multivalent coordination of the five sulfur atoms to gold with the peripheral alkyl or aryl substituents pointing away from the surface. No dissociation of C-S bonds upon binding could be observed at room temperature. Yet, the XPS experiments reveal strong chemical bonding between the thioether groups and gold. Temperature-dependent XPS study shows that the thermal stability of the monolayers is higher than the typical stability of self-assembled monolayers (SAMs) of thiolates on gold.


Assuntos
Ouro/química , Hidrocarbonetos Policíclicos Aromáticos/química , Sulfetos/química , Espectroscopia Fotoeletrônica , Temperatura
17.
Angew Chem Int Ed Engl ; 52(10): 2667-72, 2013 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-23344917
18.
Chem Commun (Camb) ; 48(44): 5425-7, 2012 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-22543307

RESUMO

The Cu(I)-catalyzed Ullmann condensation reaction between aliphatic alcohols and sym-pentachlorocorannulene provides a convenient entry to 1,3,5,7,9-pentaalkoxycorannulenes. The latter are easily converted to novel deca-heterosubstituted derivatives, such as 1,3,5,7,9-penta-X-2,4,6,8,10-penta-Y-corannulenes by electrophilic aromatic substitution.


Assuntos
Hidrocarbonetos Policíclicos Aromáticos/química , Álcoois/química , Catálise , Cobre/química , Estrutura Molecular , Estereoisomerismo
19.
Chemistry ; 18(18): 5589-605, 2012 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-22434704

RESUMO

Bistable rotaxanes are important design elements of molecular devices for a broad range of applications, such as controlled drug release, molecular rotary motors, and chemical sensors. The host-guest complexes of cucurbit[6]uril and 1,4-bis(alkylaminomethyl)benzene were found to exhibit two stable binding modes with an unexpectedly high barrier between them. Their structural and dynamic properties, kinetic and thermodynamic parameters, as well as different chemical reactivity towards the azide-alkyne [3+2] cycloaddition reaction (click chemistry), were discovered by NMR spectroscopy, X-ray crystallography, and isothermal titration microcalorimetry. The highly stable 2:1 complex, which is formed at room temperature, was found to be a kinetic product, which may be converted to the thermodynamic 1:1 complex upon prolonged heating to 100 °C. The latter is a very stable rotaxane despite the fact that it lacks bulky end groups.


Assuntos
Compostos Macrocíclicos/química , Rotaxanos/química , Sítios de Ligação , Química Click , Cristalografia por Raios X , Modelos Moleculares , Termodinâmica
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