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We developed a voltage-sensitive artificial transmembrane channel by mimicking the dipolar structure of natural alamethicin channel. The artificial channel featured a zwitterionic structure and could undergo voltage-driven flipping in the lipid bilayers. Importantly, this flipping of the channel could lead to their directional alignment in the bilayers and rectifying behavior for ion transport.

Artificial aquaporins are synthetic molecules that mimic the structure and function of natural aquaporins (AQPs) in cell membranes. The development of artificial aquaporins would provide an alternative strategy for treatment of AQP-related diseases. In this report, an artificial aquaporin has been constructed from an amino-terminated tubular molecule, which operates in a unimolecular mechanism. The artificial channel can work in cell membranes with high water permeability and selectivity rivaling those of AQPs. Importantly, the channel can restore wound healing of the cells that contain function-lost AQPs.

A new series of hydrogen-bonded helical aromatic hydrazide oligomers and polymer that bear phenylalanine tripeptide chains have been designed and synthesized. It was revealed that the helical structures could insert into lipid bilayers to form unimolecular channels. The longest oligomeric and polymeric helical channels exhibited an NH4(+)/K(+) selectivity that was higher than that of natural gramicidin A, whereas the transport of a short helical channel for Tl(+) could achieve an efficiency as high as that of gramicidin A.

The self-assembly of well-defined 2D supramolecular polymers in solution has been a challenge in supramolecular chemistry. We have designed and synthesized a rigid stacking-forbidden 1,3,5-triphenylbenzene compound that bears three 4,4'-bipyridin-1-ium (BP) units on the peripheral benzene rings. Three hydrophilic bis(2-hydroxyethyl)carbamoyl groups are introduced to the central benzene ring to suppress 1D stacking of the triangular backbone and to ensure solubility in water. Mixing the triangular preorganized molecule with cucurbit[8]uril (CB[8]) in a 2:3 molar ratio in water leads to the formation of the first solution-phase single-layer 2D supramolecular organic framework, which is stabilized by the strong complexation of CB[8] with two BP units of adjacent molecules. The periodic honeycomb 2D framework has been characterized by various (1)H NMR spectroscopy, dynamic light scattering, X-ray diffraction and scattering, scanning probe and electron microscope techniques and by comparing with the self-assembled structures of the control systems.

Peptide-appended pillar[n]arene (n = 5, 6) derivatives have been synthesized. (1)H NMR and IR studies revealed that the molecules adopt a tubular conformation in solution and lipid bilayer membranes. Kinetic measurements using the fluorescent labeling method with lipid vesicles revealed that these molecules can efficiently mediate the transport of amino acids across lipid membranes at a very low channel-to-lipid ratio (EC(50) = 0.002 mol %). In several cases, chiral selectivity for amino acid enantiomers was achieved, which is one of the key functions of natural amino acid channels.

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.

A novel type of chiral layered supramolecular copolymer with high molecular weight has been assembled from a hydrogen bonded C(6)-symmetric zinc porphyrin hexamer and chiral C(3)-symmetric pyridine hexadentate linkers driven by multivalent zinc porphyrin-pyridine coordination. UV-vis, circular dichroism, and static light scattering experiments revealed that the formation of the layered supramolecular copolymers is at first dynamically controlled and then becomes thermodynamically controlled.

This paper reports a systematic study of the dynamic process for the self-assembly of chiral organogels from achiral hydrogen bonded hydrazide foldamers by induction of chiral glucose. Six foldamers incorporated with six decyl chains and two benzene, naphthalene, anthracene, or pyrene units at the ends are revealed to strongly gelate apolar and polar solvents, including alkanes, arenes, esters, alcohols, and 1,4-dioxane. The gels are characterized by UV-vis, fluorescent, XRD, SEM, and AFM methods, based on which a dislocated "tail-to-tail" stacking pattern is proposed. Addition of octylated glucose considerably enhances the capacity of the foldamers to gelate apolar solvents due to strong complexation. The complexation also causes unique dynamic helicity induction in the gels, which is studied systematically by circular dichroism. The results are treated with the Avrami theory according to a reported method (J. Am. Chem. Soc. 2005, 127, 4336), which suggests that the gelation involves a nucleation-elongation mechanism. In addition, the "Sergeants and Soldiers" effect in the gel phase is also revealed.

This paper describes the synthesis and characterization of the first series of hydrogen bonding-driven hydrazide foldamers and their recognition for alkyl saccharides in chloroform. Oligomers 1, 2-4, 5, 6, and 7, which contain one, two, four, six, or twelve repeated dibenzoyl hydrazide residues, respectively, have been prepared. The rigid and planar conformations of 1 and 2 or 4 have been established with X-ray analysis and (1)H NMR spectroscopy, whereas the folding and helical conformations of 5-7 have been evidenced by the 1D and 2D (1)H NMR and IR spectroscopy and molecular mechanics calculations. Molecular mechanics calculations also revealed that 5, 6, and 7 possess a rigid cavity with size of ca. 10.6 to 11.1 A, and half of the carbonyl groups in the folding conformations are orientated inwardly inside the cavity. (1)H NMR and CD experiments revealed that 5-7 efficiently complex alkylated mono- and disaccharides 32-35 in chloroform. The association constants (K(assoc)) of the complexes have been determined with the (1)H NMR and fluorescent titration methods. The energy-minimized conformation of 6.34 has been obtained with molecular mechanics calculation. The hydrazide-based folding structures described here represent novel examples of hydrogen bonding-driven foldamers that act as artificial receptors for selective molecular recognition.

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.

This paper describes the synthesis, self-assembly, and characterization of a new class of highly stable hydrazide-based quadruply hydrogen-bonded heterodimers. All of the hydrazide-derived heterodimers possess the complementary ADDA-DAAD hydrogen-bonding sequences. Hydrazide derivatives 1, which has two intramolecular S(6) RO.H-N hydrogen bonds, and 2 complex to afford two fastly exchanging isomeric heterodimers 1.2 and 1.2' in chloroform, as a result of two different conformational arrangements of 2. An average binding constant K(assoc) of 4.7 x 10(4) M(-)(1) was determined for heterodimer 1.2 and 1.2' by (1)H NMR titration of 1 with changing 2 in chloroform-d. In contrast, 1 binds 11 and 12, both of which are introduced with two intramolecular S(6) hydrogen bonds, to exclusively afford heterodimers 1.11 and 1.12, with K(assoc) values of 1.8 x 10(4) and 5.0 x 10(2) M(-)(1), respectively. Fluorine-containing 19, which has a hydrazide skeleton identical to that of 1 but two intramolecular S(6) F.H-N hydrogen bonds, can also complex with 2, 11, and 12, to afford heterodimers 19.2, 19.2', 19.11, and 19.12, with K(assoc) values of of 1.2 x 10(4) (average value for 19.2 and 19.2'), 5.4 x 10(3), and 1.9 x 10(2) M(-)(1), respectively. The structures of the new heterodimers have been proven with NOESY, IR, and VPO (for some of the heterodimers) experiments. Moreover, 1 and 19 can also strongly bind 2,7-dilauroylamido-1,8-naphthyridine 23 to afford dimers 1.23 and 19.23 with K(assoc) values of 6.0 x 10(5) and 1.4 x 10(5) M(-)(1), respectively. Adding 1 to the 1:1 solution of 23 and 1-octyl-3-(4-oxo-3,4-dihydro-pyrido[2,3-d]pyrimidin-2-yl)urea 24 or 1-octyl-3-(4-oxo-1,4-dihydro-pyrimidin-2-yl)urea 25, which had been developed initially by Zimmerman and Meijer, respectively, induces dimers 23.24 and 23.25 to dissociate, leading to the formation of dimers 1.23 and 24.24 or 25.25, respectively. The new hydrazide-based hydrogen-bonding modules described are useful building blocks for self-assembly and open a new avenue to recognition between discrete supramolecular species.

Nonamphiphilic, hydrogen-bonded hydrazide foldamers appended with four or six long flexible chains were revealed to spontaneously assemble to form vesicles in methanol and organogels in aliphatic hydrocarbons. SEM, AFM, TEM, DLS, and fluorescence microscopy were all used to identify the structures of the vesicles. It was proposed that intermolecular pi stacking of the folded frameworks and hydrogen bonding of the amide units in the appended chains induced the molecules to produce cylindrical aggregates. In polar methanol, these aggregates packed together to generate one-layered vesicles owing to hydrophobically induced entanglement of the peripheral chains, while in nonpolar hydrocarbons, the peripheral chains entwined across stacked cylinders to form three-dimensional networks and thus immobilize the liquid molecules.