Using a kinase/phosphatase switch to regulate a supramolecular hydrogel and forming the supramolecular hydrogel in vivo

We have designed and synthesized a new hydrogelator Nap-FFGEY (1), which forms a supramolecular hydrogel. A kinase/phosphatase switch is used to control the phosphorylation and dephosphorylation of the hydrogelator and to regulate the formation of supramolecular hydrogels. Adding a kinase to the hydrogel induces a gel-sol phase transition in the presence of adenosine triphosphates (ATP) because the tyrosine residue is converted into tyrosine phosphate by the kinase to give a more hydrophilic molecule of Nap-FFGEY-P(O)(OH)(2) (2); treating the resulting solution with a phosphatase transforms 2 back to 1 and restores the hydrogel. Electron micrographs of the hydrogels indicate that 1 self-assembles into nanofibers. Subcutaneous injection of 2 in mice shows that 80.5 +/- 1.2% of 2 turns into 1 and results in the formation of the supramolecular hydrogel of 1 in vivo. This simple biomimetic approach for regulating the states of supramolecular hydrogels promises a new way to design and construct biomaterials.     

Synthesis, manipulation and conductivity of supramolecular polymer nanowires

The synthesis of supramolecular conducting nanowires can be achieved by using DNA and pyrrole. Oxidation of pyrrole in DNA-containing solutions yields a material that contains both the cationic polypyrrole (PPy) and the anionic DNA polymers. Intimate interaction of the two polymer chains in the self-assembled nanowires is indicated by FTIR spectroscopy. AFM imaging shows individual nanowires to be continuous, approximately 5 nm high and conformationally flexible. This feature allows them to be aligned by molecular combing in a similar manner to bare DNA and provides a convenient method for fabricating a simple electrical device by stretching DNA/PPy strands across an electrode gap. Current-voltage measurements confirm that the nanowires are conducting, with values typical for a polypyrrole-based material. In contrast to polymerisation of pyrrole on a DNA template in bulk solution, attempts to form similar wires by polymerisation at surface-immobilised DNA do not give a continuous coverage; instead, a beads-on-a-string appearance is observed suggesting that immobilisation inhibits the assembly process.     

Single-crystal nanoribbons, nanotubes, and nanowires from intramolecular charge-transfer organic molecules

Single-crystal one-dimensional (1-D) nanostructures of [2-(p-dimethyl-aminophenyl)ethenyl]-phenyl-methylene-propanedinitrile (DAPMP) have been prepared by a simple solution process without the assistance of added surfactant, catalyst, or template under ambient condition. The approach exploits the directional supramolecular interaction induced by strong donor-acceptor dipole-dipole supramolecular interaction in the growth of 1-D nanostructures. By varying the process temperatures, the DAPMP nanostructures can be controllably prepared as either nanoribbons, nanotubes, or nanowires with high morphological and chemical purities. Significant changes in optical properties were observed for nanostructures of different morphology.     

Assemblies of redox-active metallodendrimers using hydrogen bonding for the electrochemical recognition of the H2PO4- and adenosine-triphosphate (ATP2-) anions

Two families of five metallodendrimers have been assembled by hydrogen bonding between the primary amino groups of DSM dendrimers G(n)-DAB-dendr-(NH(2))x (n = 1-5; x = 4, 8, 16, 32, 64) and the OH group of phenol dendrons containing a triallyl or a triferrocenylalkyl tripod in para position. These H-bonded dendrimers noted G(1)-DAB-12Fc, G(2)-DAB-24Fc, G(3)-DAB-48Fc, G(4)-DAB-96Fc, and G(5)-DAB-192Fc have been characterized as resulting from fast, reversible hydrogen bonding by the single broad signal observed in (1)H NMR for the three NH(2) + OH protons whose location depends on the concentration. The cyclic voltammograms (CVs) show a single reversible ferrocenyl wave due to the equivalence of these groups and the fast rotation of the supramolecular ensemble compared to the CV time scale. A new CV wave appears at less anodic potential upon addition of H(2)PO(4)(-) or adenosine-triphosphate (ATP(2)(-)) anion as a tetrabutylammonium salt as with previously studied ferrocenyl dendrimers. In addition, other specific and remarkable features are the fact that the new CV wave is much less intense than the initial one and the dramatically sudden disappearance of the initial CV wave at the equivalent point indicating the formation of a large supramolecular assembly with the hydrogenophosphate groups. Finally, the variation of the number of equivalent anions with the generation number to reach the equivalent point also suggests that the competition between the amino- and amido group for the interaction with hydrogenophosphate depends on the generation number. Recognition by these supramolecular dendrimers of H(2)PO(4)(-) and ATP(2)(-) follows the model of the relatively strong-interaction type in the Kaifer-Echegoyen model, which allows access to the ratio of association constants K(+)/K(0). A positive dendritic effect is found for the recognition of H(2)PO(4)(-) (i.e., the difference of potentials DeltaE(1/2) between the initial CV wave and the new one and the K(+)/K(0) value increase as the generation number increases) whereas the dendritic effect is slightly negative for the recognition of ATP(2)(-).     

From Interaction to Function in DNA-Templated Supramolecular Self-Assemblies

DNA-templated self-assembly represents a rich and growing subset of supramolecular chemistry where functional self-assemblies are programmed in a versatile manner using nucleic acids as readily-available and readily-tunable templates. In this review, we summarize the different DNA recognition modes and the basic supramolecular interactions at play in this context. We discuss the recent results that report the DNA-templated self-assembly of small molecules into complex yet precise nanoarrays, going from 1D to 3D architectures. Finally, we show their emerging functions as photonic/electronic nanowires, sensors, gene delivery vectors, and supramolecular catalysts, and their growing applications in a wide range of area from materials to biological sciences.     

Templated Synthesis of CdS/PAN Composite Nanowires under Ambient Conditions

CdS/PAN (polyacrylonitrile) composite nanowires were prepared by templated synthesis under ambient conditions, using a 4 : 1 (v/v) distilled water-isopropyl alcohol solvent mixture and Na(2)S(2)O(3) as sulfur source. Transmission electron microscopy images showed typical CdS/PAN nanowires with diameters less than 6 nm and lengths from 200 nm to 1 μm. CdS/PAN nanowires were also characterized by FT-infrared spectra (FTIR), X-ray powder diffraction (XRD) patterns, and UV-vis spectra. It is found that the feed mole ratio of CdCl(2) to AN exerts a significant influence on the formation and morphology of CdS/PAN nanowires. In addition, possible mechanism of the reactive process was presented. Copyright 2000 Academic Press.     

Bottom‐up Assembly of Poly(3‐hexylthiophene) on Carbon Nanotubes: 2D Building Blocks for Nanoscale Circuits

Hierarchical poly(3‐hexylthiophene)(P3HT)/carbon nanotube (CNT) supramolecular structures were fabricated through a bottom‐up CNT induced P3HT crystallization strategy. P3HT nanowires growing perpendicular from CNT surface have uniform width and height. The density and the length of these nanowires can be controlled by tuning the P3HT/CNT mass ratio. The quasi‐isothermal crystallization process monitored by in situ UV–Vis spectroscopy indicates that CNTs can greatly enhance the P3HT crystallization, and the P3HT nanowire formation follows first‐order kinetics. Such bottom‐up strategy provides a general approach to build 2D functional conductive supramolecular structures that will lead to numerous applications in nanoscale electronics.

     

The solventless syntheses of unique PbS nanowires of X-shaped cross sections and the cooperative effects of ethylenediamine and a second salt

Unique PbS nanowires with x-shaped cross sections, with diameters in the range of 300-800 nm with an average of 598 nm (sigma = +/-21.7% ), and lengths of up to several tens of micrometers, have been made by a solventless method. Such nanowires show high adsorptivities of the PbS nanooctahedra, which can be washed off by ultrasound. The suitable precursor is obtained from a Pb(NO3)2/octanoate/ethylenediamine/dodecanethiol molar ratio of 1:2:1:1.6, and the PbS nanowires are produced by the thermolysis of such precursors at 280 degrees C for 1 hour. The X-ray diffraction, scanning electron microscopy, and transmission electron microscopy characterizations of the products and the keys of the morphological control have been reported. For the formation of such products, two cooperative effects are found to be crucial, the roles of ethylenediamine and a second salt, lead octanonate.     

模板法制备枝状Pt纳米线

一维纳米材料的制备是近年来纳米材料的研究热点. 利用具有纳米尺度的孔洞阵列模板沉积各种材料构筑纳米线的方法具有制备简便和成本较低等优点[1,2]. 常用的模板有多孔阳极氧化铝(AAO)、多孔硅和聚合物等, 其中AAO模板具有耐高温, 绝缘性好, 孔洞分布均匀, 孔径、孔深大小可控等特点, 是模板法研究的热点. 通过模板法电化学沉积制备各种金属纳米线已有很多报道[3～8], 本研究小组也曾报道了模板法电化学沉积Au等纳米线的制备及性质[9～12], 但用该方法制备的金属纳米线都为单一的线状结构. 组成当代大规模集成电路的基本器件一般具有3个或3个以上的电极. 单一的线状结构纳米线, 不能满足纳米电子学对纳米材料和纳米器件性能研究的需要. 在纳米器件的特性研究和探索中, 枝状或Y形纳米结的制备有重要的意义, 它是纳米器件从理论到实用化的必备条件. Sui等[13]用模板法成功制备了枝状碳纳米管, 但用AAO模板制备枝状金属纳米线的研究至今还未见报道. 本文通过控制铝片的阳极氧化条件, 先制备出具有分枝状孔洞结构的AAO模板, 再用电化学法沉积金属Pt, 实现了枝状Pt纳米线的可控生长. 这对其它金属枝状纳米线的制备以及进一步掺杂、构筑纳米原型器件等具有显著的实用价值.     

Fabrication of polydiacetylene nanowires by associated self-polymerization and self-assembly processes for efficient field emission properties

The paper described here concerns a challenge of general interest for producing a novel structure of a polymer aggregate, the achievement of nanowires with controlled diameters. We provide a strategy for fabricating a supramolecular polymer, in which ordered polydiacetylene nanowires can be obtained by associated self-polymerization and self-assembly processes. The polymer nanowire film shows excellent field emission properties with the turn-on field of 8.2 V/mum at 10 muA/cm2 and the maximum current density of 5 mA/cm2 at an applied field of 15 V/mum.     

Differential effects of Mg(ii) and N(alpha)-4-tosyl-l-arginine methyl ester hydrochloride on the recognition and catalysis in ATP hydrolysis

The supramolecular interactions of Mg(ii) and N(alpha)-4-tosyl-l-arginine methyl ester hydrochloride (TAME) with ATP have been investigated using (1)H and (31)P NMR spectra. Furthermore, the hydrolysis of ATP catalyzed by Mg(ii) and TAME has been studied at 60 degrees C and pH 7 using (31)P NMR spectra. In the Mg(ii)-ATP-TAME ternary system, the binding interaction of Mg(2+) with ATP involves not only N1 and N7 in the adenine ring but also beta- and gamma-phosphate of ATP. The binding forces are mainly electrostatic interaction and cation (Mg(2+))-pi interaction. The guanidinium group and the aromatic ring of TAME interacts with ATP by beta and gamma phosphate and the adenine ring of ATP. The binding forces are mainly electrostatic interactions and pi-pi stacking. A significant difference between the binary and the ternary system indicates that TAME is essential to the stablization of the intermediate. Kinetic studies show that the hydrolysis rate constant of ATP is 2.16 x 10(-2) h(-1) at pH 7 in the Mg(ii)-TAME-ATP ternary system. The Mg(ii) ion and TAME can accelerate the ATP hydrolysis process. A possible mechanism has been proposed that the hydrolysis occurs through an addition-elimination, in which the phosphoramidate intermediate was observed at 3.21 ppm in the (31)P NMR of the ternary system. These results provide further information concerning the effect of the key amino acid residue and metal ions as cofactors of ATPase on ATP synthesis/hydrolysis at the molecular level.     

Time-encoded bio-fluorochromic supramolecular co-assembly for rewritable security printing

Innovative fluorescence security technologies for paper-based information are still highly pursued nowadays because data leakage and indelibility have become serious economic and social problems. Herein, we report a novel transient bio-fluorochromic supramolecular co-assembly mediated by a hydrolytic enzyme (ALP: alkaline phosphatase) towards rewritable security printing. A co-assembly based on the designed tetrabranched cationic diethynylanthracene monomer tends to be formed by adding adenosine triphosphate (ATP) as the biofuel. The resulting co-assembly possesses a time-encoded bio-fluorochromic feature, upon successively hydrolyzing ATP with ALP and re-adding new batches of ATP. On this basis, the dynamic fluorescent properties of this time-encoded co-assembly system have been successfully enabled in rewritable security patterns via an inkjet printing technique, providing fascinating potential for fluorescence security materials with a biomimetic mode.

Rewritable security printing has been successfully achieved based on a biofuel-driven transient supramolecular co-assembly mediated by an enzyme, providing fascinating potential for artificial functional materials with a biomimetic mode.     

Quantum Dots Arrangement and Energy Transfer Control via Charge‐Transfer Complex Achieved on Poly(Phenylene Ethynylene)/Schizophyllan Nanowires

Assemblies of organic and inorganic compounds in the nanoscale region have contributed to the development of novel functional materials toward future applications, including sensors and opto‐electronics. We succeed in fabricating hybrid nanowires composed of a conjugated polymer and semiconductor quantum dots (QDs) by a supramolecular assembly technique. The 1‐D fashion of the nanowire structure is obtained by the polymer wrapping of cationic poly(phenylene ethynylene) (PPE) with helix‐forming polysaccharide schizophyllan (SPG). The electrostatic interaction between cationic PPE and anionic QDs affords the nanowires decorated with QDs. Upon addition of an acceptor molecule, tetranitrofluorenone (TNF), the charge‐transfer (CT) complex between PPE and TNF is formed, resulting in energy transfer from the QDs to PPE arising from the induced spectral overlap. Furthermore, the employment of the conjugated polymer allows highly sensitive quenching of the QD’s emission by raising the transmission efficiency to the CT complexed electron deficient sites along the polymer backbone.     

Thermoresponsive Supramolecular Dendronized Polymers

Combining the concepts of supramolecular polymers and dendronized polymers provides the opportunity to create bulky polymers with easy structural modification and tunable properties. In the present work, a novel class of side‐chain supramolecular dendronized polymethacrylates is prepared through the host–guest interaction. The host is a linear polymethacrylate (as the backbone) attached in each repeat unit with a β‐cyclodextrin (β‐CD) moiety, and the guest is constituted with three‐fold branched oligoethylene glycol (OEG)‐based first‐ (G1) and second‐generation (G2) dendrons with an adamantyl group core. The host and guest interaction in aqueous solution leads to the formation of the supramolecular polymers, which is supported with ¹H NMR spectroscopy and dynamic light scattering measurements. The supramolecular formation was also examined at different host/guest ratios. The water solubility of hosts and guests increases upon supramolecular formation. The supramolecular polymers show good solubility in water at room temperature, but exhibit thermoresponsive behavior at elevated temperatures. Their thermoresponsiveness is thus investigated with UV/Vis and ¹H NMR spectroscopy, and compared with their counterparts formed from individual β‐CD and the OEG dendritic guest. The effect of polymer concentration and molar ratio of host/guest was examined. It is found that the polar interior of the supramolecules contribute significantly to the thermally‐induced phase transitions for the G1 polymer, but this effect is negligible for the G2 polymer. Based on the temperature‐varied proton NMR spectra, it is found that the host–guest complex starts to decompose during the aggregation process upon heating to its dehydration temperature, and this decomposition is enhanced with an increase of solution temperature.     

Three self-penetrated, interlocked, and polycatenated supramolecular isomers via one-pot synthesis and crystallization

Three supramolecular isomers, {[Cd(2)(TPOM)(hfipbb)(2)]·x/y/zsolvent}(n) (1-3), have been synthesized and characterized by one-pot reaction. Even though the compositions of 1-3 are the same, they generate different structures. Reactions over various time periods were found to influence the formation of supramolecular isomers, and there is little influence on this system under other conditions.     

A new molecular scaffold for the formation of supramolecular peptide double helices: the crystallographic insight

[structure: see text]. A series of water-soluble synthetic dipeptides (1-3) with an N-terminally located beta-alanine residue, beta-alanyl-l-valine (1), beta-alanyl-l-isoleucine (2), and beta-alanyl-l-phenylalanine (3), form hydrogen-bonded supramolecular double helices with a pitch length of 1 nm, whereas the C-terminally positioned beta-alanine containing dipeptide (4), l-phenylalanyl-beta-alanine, does not form a supramolecular double helical structure. beta-Ala-Xaa (Xaa = Val/Ile/Phe) can be regarded as a new motif for the formation of supramolecular double helical structures in the solid state.     

Ultralong cadmium hydroxide nanowires: synthesis, characterization, and transformation into CdO nanostrands

Ultralong Cd(OH)2 nanowires were fabricated by a hydrothermal method from Cd(CH3COO)2 x H2O (0.01 mol/L) and C6H12N4 (0.015 mol/L) aqueous solution at 95 degrees C for 16 h without using any templates and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). The length of the nanowires reached several micrometers, giving an aspect ratio of a few thousands. The formation mechanism of the nanowires is attributed to the oriented attachment of small particles. The growth method for the 1D nanostructure presented here offers an excellent tool for the design of other advanced materials with anisotropic properties. The Cd(OH)2 nanowires efficiently captured negatively charged dye, and the adsorbed dye molecules can be released after the addition of EDTA. The Cd(OH)2 nanowires as template compounds were further transformed into CdO semiconductor nanomaterials with similar morphology by calcination under 350 degrees C in air for 3 h.     

Real-time and in-situ intracellular ATP assay with polyimidazolium brush-modified nanopipette

The level and dynamics of adenosine 5'-triphosphate(ATP) in single living cells are closely related to many kinds of important physiological and pathological processes. Herein, we report a nanosensor based on polyimidazolium brush(PimB)-modified nanopipette for intracellular ATP assay, which shows good selectivity, high spatiotemporal resolution and excellent stability.Both the specific supramolecular interaction between polyimidazolium and ATP, and the rationally tunable property of the ion transport at a confined nanopipette enable the selective assay of ATP even in complex intracellular environment. Moreover, the tiny tip(ca.300 nm) and the low polarized current(e.g., 1 nA) essentially make the as-prepared nanosensor safe to the living cells. The nanosensor is demonstrated to be useful for in-situ monitoring the basal ATP levels of chromaffin cells from wild-type mice and DJ-1 knockout mice, and for real-time monitoring the metabolism process of intracellular ATP.     

Modular design of an ultrahigh-intensity nanoparticle probe for cancer cell imaging and rapid visual detection of nucleic acids

Based on a modular design, a novel ultrahigh-intensity nanoparticle probe was synthesized by orderly assembling supramolecular DNA/CdTe quantum dot nanowires and recognition DNA sequences on polystyrene microbeads. The probe was successfully applied to cancer cell imaging and visual detection of nucleic acids.     

Supramolecular polymerization of electronically complementary linear motifs: anti-cooperativity by attenuated growth

Anti-cooperative supramolecular polymerization by attenuated growth exhibited by self-assembling units of two electron-donor benzo[1,2-b:4,5-b′]dithiophene (BDT) derivatives (compounds 1a and 1b) and the electron-acceptor 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) (compound 2) is reported. Despite the apparent cooperative mechanism of 1 and 2, AFM imaging and SAXS measurements reveal the formation of small aggregates that suggest the operation of an anti-cooperative mechanism strongly conditioned by an attenuated growth. In this mechanism, the formation of the nuclei is favoured over the subsequent addition of monomeric units to the aggregate, which finally results in short aggregates. Theoretical calculations show that both the BDT and BODIPY motifs, after forming the initial dimeric nuclei, experience a strong distortion of the central aromatic backbone upon growth, which makes the addition of successive monomeric units unfavourable and impedes the formation of long fibrillar structures. Despite the anti-cooperativity observed in the supramolecular polymerization of 1 and 2, the combination of both self-assembling units results in the formation of small co-assembled aggregates with a similar supramolecular polymerization behaviour to that observed for the separate components.

The anti-cooperative supramolecular polymerization of compounds 1 and 2, in which the formation of the nuclei is favoured over the growth of the aggregate, is investigated. Despite this anti-cooperativity 1 and 2 can afford co-assembled aggregates.