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ABSTRACT: Peptide-appended pillar[n]arene (n = 5, 6) derivatives have been synthesized. 1H NMR and IR studies reveal that the molecules adopt a tubular conformation in solution and lipid bilayer membranes. Kinetic measurements using the fluorescent labeling method with lipid vesicles reveals that these molecules can efficiently mediate the transport of amino acids across lipid membranes at a very low channel-to-lipid ratio (EC50 = 0.002 mol%) and, in several cases, chiral selectivity for amino acid enantiomers can be achieved, which features one of the key functions of natural amino acid channels.
Journal of the American Chemical Society 01/2013; 135(6):2152-2155. · 9.91 Impact Factor
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ABSTRACT: Pillar[5]arenes with introverted amino groups were produced through aminolysis. X-ray analysis demonstrated that the intramolecular hydrogen bonding induced the amino group toward the inner space of the cavity. The kinetic studies and molecular modelings revealed that the hydrogen bonding also contributed to the acceleration of the aminolysis through stabilizing the intermediate.
Organic & Biomolecular Chemistry 11/2012; · 3.70 Impact Factor
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Chemical Reviews 08/2012; 112(10):5271-316. · 40.20 Impact Factor
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ABSTRACT: Hydrazide-appended pillar[5]arene derivatives have been synthesized. X-ray crystal structure analysis and (1)H NMR studies revealed that the molecules adopt unique tubular conformations. Inserting the molecules into the lipid membranes of vesicles leads to the transport of water through the channels produced by single molecules, as supported by dynamic light scattering and cryo-SEM experiments. The channels exhibit the transport activity at a very low channel to lipid ratio (0.027 mol %), and a water permeability of 8.6 × 10(-10) cm s(-1) is realized. In addition, like natural water channel proteins, the artificial systems also block the transport of protons.
Journal of the American Chemical Society 05/2012; 134(20):8384-8387. · 9.91 Impact Factor
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ABSTRACT: Three pillar[n]arenes (n = 8-10) were synthesized. X-ray analysis demonstrated that, different from early reported small pillar[n]arenes (n = 5, 6), these larger macrocycles gave rise to two cavities. (1)H NMR and MS experiments revealed that pillar[9]arene complexed one n-octyltrimethyl ammonium in chloroform, while pillar[10]arene could complex two.
Chemical Communications 01/2012; 48(89):10999-11001. · 6.17 Impact Factor
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ABSTRACT: Lined up water molecules: Artificial transmembrane channels from pillar[5]arene monomeric and dimeric derivatives have been prepared. Single-channel conductance measurements and isotope effect experiments under acidic conditions showed selective proton transport through the channels, which were mediated by water wires formed in the pillar[5]arene backbones (see picture).
Angewandte Chemie International Edition 11/2011; 50(52):12564-8. · 13.45 Impact Factor
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ABSTRACT: A pillar[5]arene decaamine has been synthesized and revealed to encapsulate linear diacids in neutral, alkaline, and acidic conditions, driven by the hydrophobic and electrostatic interactions, to give rise to pseudo[2]rotaxanes. Ion pair-bonded stoppers can further lock the diacids to generate stable water soluble [2]rotaxanes.
Chemical Communications 03/2011; 47(16):4694-6. · 6.17 Impact Factor
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ABSTRACT: A semi-static test of Pb exposure (0, 0.2, 0.8, and 1.6 mg L(-1)) was carried out to examine the Pb accumulation and elimination in different tissues of juvenile Chinese sturgeon (Acipenser sinensis). With increasing Pb concentration in water, the Pb concentration in juvenile A. sinensis tissues increased, showing a clear dose-response relationship. The Pb accumulation had a trend of being higher in bone (dorsalbone plate and cartilaginous bone) and muscle, followed by in stomach, intestine, and skin, and relatively low in liver, gill, and notochord. A 6-week duration test after Pb exposure showed that in low dose group (0.2 mg x L(-1)), the Pb concentration in all tissues had no significant differences to the control group, but in medium dose group (0.8 mg x L(-1)), the Pb concentration in most tissues except gill stomach, cartilaginous bone, and muscle was significantly higher than the control. In high dose group (1.6 mg x L(-1)), the Pb concentration in the tissues other than liver, intestine and skin was significantly higher than the control. Through the comparison of accumulation and elimination, it was found that after low- and medium dose exposure, the Pb concentration in skin, gill, and liver was higher than its accumulation, presuming that Pb was absorbed from gill, skin, and alimentary canal, and eliminated from gill and skin.
Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban 02/2010; 21(2):476-82.
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ABSTRACT: Self-assembled capsules are nanoscale structures made up of multiple synthetic subunits held together by weak intermolecular
forces. They act as host structures that can completely surround small molecule guests of the appropriate size, shape and
chemical surface. Like their biological counterparts, multimeric enzymes and receptors, the subunits of the capsules are generally
identical, and lead to homomeric assemblies of high symmetry. In both biological and synthetic systems small variations in
structures are tolerated and lead to heteromeric assemblies with slightly different recognition properties. The synthetic
capsules are dynamic, with lifetimes from milliseconds to hours, and allow the direct spectroscopic observation of smaller
molecules inside, under ambient conditions at equilibrium in solution. We report here the assembly of hybrid capsules made
up of 2 very different structures, both capable of forming their own homomeric capsules through hydrogen bonding. These hybrids
exhibit host properties that differ markedly from the parent capsules, and suggest that other capsules may emerge from seemingly
unrelated modules that have curved surfaces and are rich in hydrogen bonding capabilities.
Proceedings of the National Academy of Sciences 06/2009; 106(26):10430-10434. · 9.68 Impact Factor
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ABSTRACT: Self-assembled capsules are nanoscale structures made up of multiple synthetic subunits held together by weak intermolecular forces. They act as host structures that can completely surround small molecule guests of the appropriate size, shape and chemical surface. Like their biological counterparts, multimeric enzymes and receptors, the subunits of the capsules are generally identical, and lead to homomeric assemblies of high symmetry. In both biological and synthetic systems small variations in structures are tolerated and lead to heteromeric assemblies with slightly different recognition properties. The synthetic capsules are dynamic, with lifetimes from milliseconds to hours, and allow the direct spectroscopic observation of smaller molecules inside, under ambient conditions at equilibrium in solution. We report here the assembly of hybrid capsules made up of 2 very different structures, both capable of forming their own homomeric capsules through hydrogen bonding. These hybrids exhibit host properties that differ markedly from the parent capsules, and suggest that other capsules may emerge from seemingly unrelated modules that have curved surfaces and are rich in hydrogen bonding capabilities.
Proceedings of the National Academy of Sciences 03/2009; 106(26):10430-4. · 9.68 Impact Factor
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ABSTRACT: This paper reports the gelation and liquid crystal properties of a class of new complexes between zinc and copper bisporphyrin and C60 derivatives. The bisporphyrins are induced by intramolecular hydrogen bonding to adopt a preorganized ‘U’-shaped conformation and therefore efficiently complex the C60 derivatives. As a result, the capacity of their mixtures to gelate alkanes is increased notably. The bisporphyrins themselves and their complexes with the C60 derivatives form the smectic liquid crystal phase. However, the glassy transition temperature of the complexes decreases considerably.Graphical abstract
Tetrahedron. 01/2009; 65(49):10182-10191.
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ABSTRACT: In this paper, we report the synthesis and self-assembling behavior of an F⋯H–N hydrogen bonding-induced arylamide-based dipodal foldamer. SEM, AFM, TEM, and XRD studies reveal that this preorganized oligomer stacks to form vesicles in methanol–chloroform (10–70%) binary solvents due to the strong stacking interaction of the folded segments and the supramolecular polymeric feature of the dipodal molecule in the stacked state. In contrast, a simple folded molecule can give rise to vesicles only when the chloroform content is 45–55%.Graphical abstract
Tetrahedron. 01/2009; 65(51):10544-10551.
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ABSTRACT: Reversible encapsulation complexes are applied to the reaction of isonitriles with carboxylic acids. Encapsulation facilitates these reactions by amplifying the concentration of reactants, arranging the acid and isonitrile in the appropriate orientations, isolating intermediates from bulk solution, and providing an organized solvent cage.
Journal of the American Chemical Society 07/2008; 130(25):7810-1. · 9.91 Impact Factor
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ABSTRACT: Hydrogen-bonded oligoamide foldamers represent a large family of peptide mimics. Pioneered by Gellman and Seebach (Appella , J. Am. Chem. Soc. 1996, 118, 13071- 13072; Seebach , Helv. Chim. Acta 1996, 79, 913- 941), aliphatic amino acid-based mimic structures have been extensively studied. Results of these studies have found many useful applications in areas including chemical biology and drug design. This Account describes our efforts in creating arylamide-based foldamers whose compact conformations are stabilized by hydrogen bonding. The aim of our study was to test whether this class of mimic structures is sufficiently rigid to lead to new interesting functions. It was envisioned that, if our approach was workable, it might be developed into a new family of useful soft frameworks for studies toward molecular recognition, self-assembly, and materials science. Three classes of mimic structures, that is, folded or helical, zigzag, and straight oligomers, have been constructed by simply changing the positions of the substituents at the benzene rings in the backbones. Both amide and hydrazide units have been employed to construct the frameworks. In most cases, O...H-N hydrogen bonding was chosen to stabilize the compact conformations. Notably, for the first time the F...H-N hydrogen-bonding pattern has been used to tune the size of the cavity. To test their usefulness, these frameworks have been extensively modified and functionalized. (1)H NMR, UV-vis, fluorescence, circular dichroism, and X-ray diffraction techniques have all been employed to establish the compact structures and their interactions with guest molecules. The properties or functions of the mimic structures have been studied in seven aspects. (1) Acyclic molecular receptors: The amide foldamers can bind amine cations, while the hydrazide foldamers can complex saccharides. (2) Acceleration of anisole hydrolysis: Several folded oligomers are able to bind alkali metal cations and consequently promote the hydrolysis of the nitro-substituted anisole by alkali hydroxides. (3) Facilitation of macrocyclization: The straight and zigzag backbones can be readily functionalized, from which two classes of macrocycles have been prepared. (4) Homoduplex assembly: Zigzag oligomers that are appended with amide units at one side can form stable homoduplexes through the cooperative self-binding of the amide units. (5) Assembly of molecular tweezers: Discrete binding moieties are introduced at the ends of the oligomers, which can bind structurally matched guests. (6) Assembly of nano networks: F...H-N hydrogen-bonded foldamers can stack with fullerenes; thus a mixture of fullerenes with a trifoldamer generates honeycomb-styled nanoarchitectures. (7) Assembly of dynamic [2]catenanes: A preorganized porphyrin tweezer has been synthesized, from which dynamic three-component [2]catenanes have been assembled in high yields. Our results demonstrate that hydrogen-bonding-driven arylamide oligomers are a class of structurally unique mimic structures. The folded oligomers themselves can be used as synthetic receptors for binding different guest molecules, while incorporation of different segments into one system can produce many desired shapes. In addition, all of the rigid frameworks can be readily functionalized at specific sites. We believe that our results have helped to open the door for some new chemistry in molecular recognition, self-assembly, and other related areas.
Accounts of Chemical Research 04/2008; 41(10):1343-1353. · 21.64 Impact Factor
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ABSTRACT: Four intramolecularly F···H−N hydrogen-bonded aromatic amide and hydrazide derivatives have been prepared. Their crystal structures are investigated and compared with those of their MeO···H−N hydrogen-bonded analogues. It is found that all the F···H−N hydrogen-bonded molecules form intermolecular CO···H−N hydrogen bonding and, for two of them, weak F···H−C interactions. In contrast, the MeO···H−N hydrogen-bonded molecules display only very weak intermolecular C−H···π interactions. The hydrogen-bonded amide units in the fluorine-bearing molecules exhibit large torsion from the connecting benzene units. This has been attributed to the weaker ability of fluorine as a hydrogen-bonding acceptor, its smaller size (relative to the MeO group), and consequently the strengthened intermolecular NH···OC hydrogen bonding. The results also suggest that, although the weakness of fluorine as a hydrogen-bonding acceptor has been mainly attributed to its low polarizability and tightly contracted lone pairs, the great tendency of fluorine-bearing aromatic amides to form intermolecular CO···H−N hydrogen bonding may also play a role.
Crystal Growth & Design 07/2007; 7(8):1490-1496. · 4.72 Impact Factor
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ABSTRACT: This paper describes the self-assembly of a new class of three-component dynamic [2]catenanes, which are driven or stabilized by intramolecular hydrogen bonding, coordination, and electrostatic interaction. One of the component molecules 2, consisting of an aromatic oligoamide spacer and two peripheral zinc porphyrin units, was designed to adopt a folded preorganized conformation, which is stabilized by consecutive intramolecular three-centered hydrogen bonds. Component molecule 3 is a linear secondary ammonium bearing two peripheral pyridine units, which was designed to form a 1:1 complex with 24-crown-8 (5). The 1H NMR and UV-vis experiments in CDCl3-CD3CN (4:1 v/v) revealed that, due to the preorganized U-shaped feature, 2 could efficiently bind 3 through the cooperative zinc-pyridine coordination to generate highly stable 1:1 complex 2.3. Adding 5 to the 1:1 solution of 2 and 3 led to the formation of dynamic three-component [2]catenane 2.3.5 as a result of the threading of 3 through 5. 1H NMR studies indicated that in the 1:1:1 solution (3 mM) [2]catenane 2.3.5 was generated in 55% yield at 25 degrees C. The yield was increased with the reduction of the temperature and [2]catenane could be produced quantitatively in a 1:1:2 solution ([2]=3 mM) at -13 degrees C. Replacing 3 with 1,2-bis(4,4'-bipyridinium)ethane (4) in the three-component solution could also give rise to similar dynamic [2]catenane 2.4.5 albeit in slightly lower yield.
The Journal of Organic Chemistry 05/2007; 72(8):2897-905. · 4.45 Impact Factor
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ABSTRACT: With an increasing number of folding and helical structures available, chemists have begun to pay greater attention to the functions of this family of structurally unique oligomers. Hydrogen-bonding-mediated aromatic oligoamide foldamers have the features of good structural predictability, synthetic facility, and structural modification, which make them very promising as scaffolds or platforms for supramolecular chemistry. Recent advances in the applications of this class of shape-persistent oligomers in the promoted synthesis of macrocycles, design of new nonring receptors, supramolecular self-assembly, molecular encapsulation, and reaction acceleration, are highlighted in this Focus Review.
Chemistry - An Asian Journal 01/2007; 1(6):766-778. · 4.50 Impact Factor
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Angewandte Chemie International Edition 02/2006; 45(5):796-800. · 13.45 Impact Factor
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ABSTRACT: This paper describes the self-assembly of a new class of foldamer-based molecular tweezers, whose rigid folded conformations are stabilized by intramolecular hydrogen bonding. Two zinc porphyrin units are introduced to the ends of molecular tweezers Zn(2)1 and Zn(2)2, while three zinc porphyrin units are incorporated to the S-shaped bi-tweezers Zn(3)3, which may be regarded as a combination of two Zn(2)1 molecules. Due to the preorganized U-shaped feature, Zn(2)1 and Zn(2)2 are able to strongly complex C60, C70, and C60 derivative 25 in chloroform or toluene in a 1:1 binding stoichiometry, whereas Zn(3)3, which possesses two tweezer units, complexes the guests in a 1:2 stoichiometry. More stable complex Zn(3)3.24 is formed between Zn(3)3 and 24, a linear molecule bearing two C60 moieties at the ends, as a result of the cooperative interaction of two binding sites. Chiral induction is observed for all the three receptors upon complexation with C60-incoporated chiral phenylalanine derivative 29, although the complexation of 29 by the folding receptors is pronouncedly weaker than that of C60 and 25 due to increased steric hindrance. The driving force for the formation of the complexes is the well established pi-pi stacking between the zinc porphyrin and fullerene units. The 1H and 13C NMR, UV-vis, fluorescent, and circular dichroism spectroscopy have been used to investigate the complexing behavior of the folding receptors and the fullerene guests. The association constants of the corresponding complexes in toluene and chloroform (if possible) have been evaluated with the UV-vis and fluorescent titration experiments.
Journal of the American Chemical Society 01/2006; 127(49):17460-17468. · 9.91 Impact Factor
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Angewandte Chemie 12/2005; 118(5):810 - 814.
