Artificial tongues and leaves

The objective with synthetic multifunctional nanoarchitecture is to create large suprastructures with interesting functions. For this purpose, lipid bilayer membranes or conducting surfaces have been used as platforms and rigid-rod molecules as shape-persistent scaffolds. Examples for functions obtained by this approach include pores that can act as multicomponent sensors in complex matrices or rigid-rod π-stack architecture for artificial photosynthesis and photovoltaic

Regulated transport with synthetic ion channels and pores : anion selectivity, ligand gating and blockage

Une bibliothèque de 8 baguettes a été analysée afin de déterminer la capacité de chaque molécule à transporter les anions sélectivement. Les molécules ont montré une activité de transport variable en fonction de leurs groupements terminaux hydrophobes ou hydrophiles qui influent sur leur solubilité dans l'eau et dans les membranes ainsi que leur orientation dans les membranes. Les résultats obtenus sont en faveur d'interactions anion-[pi] entre les unités NDI des baguettes et les anions. Le baril-β LHRHL à baguettes rigides est innovant. Contrairement aux précédents barils artificiels, il s'ouvre en réponse à une stimulation chimique: la liaison d'anions amphiphiles aux origines externes. De plus, le blocage du pore a été observé en présence d'acide polyglutamique et d'héparine. Le pore permet de suivre "en direct" une estérolyse comme s'il était possible de voir les molécules réagir dans le milieu réactionnel

Hydrophilic Anchors for Transmembrane Anion-π Slides

The concept of hydrophilic anchoring is introduced to activate rigid oligonaphthalenediimide (O-NDI) rods as anion–p slides for multi-ion hopping across lipid bilayers. We report that short peptide solubilizers suffice to reach the rare combination of high activity and high selectivity that is needed for anion pumping in vesicles

Rigid-rod anion-π slides for multiion hopping across lipid bilayers

Shape-persistent oligo-p-phenylene-N,N-naphthalenediimide (O-NDI) rods are introduced as anion-pi slides for chloride-selective multiion hopping across lipid bilayers. Results from end-group engineering and covalent capture as O-NDI hairpins suggested that self-assembly into transmembrane O-NDI bundles is essential for activity. A halide topology VI (Cl > F > Br approximately I, Cl/Br approximately Cl/I > 7) implied strong anion binding along the anion-pi slides with relatively weak contributions from size exclusion (F >or= OAc). Anomalous mole fraction effects (AMFE) supported the occurrence of multiion hopping along the pi-acidic O-NDI rods. The existence of anion-pi interactions was corroborated by high-level ab initio and DFT calculations. The latter revealed positive NDI quadrupole moments far beyond the hexafluorobenzene standard. Computational studies further suggested that anion binding occurs at the confined, pi-acidic edges of the sticky NDI surface and is influenced by the nature of the phenyl spacer between two NDIs. With regard to methods development, a detailed analysis of the detection of ion selectivity with the HPTS assay including AMFE in vesicles is provided

Rigid Oligonaphthalenediimide Rods as Transmembrane Anion-π Slides

We report the design, synthesis, and evaluation of rigid oligonaphthalenediimide (O-NDI) rods that are expected to act as transmembrane anion-pi slides. Studies in fluorogenic large unilamellar egg yolk phosphatidylcholine vesicles reveal that rigid O-NDI rods mediate anion-selective transport with a rare halide VI selectivity sequence (Cl- > F- > Br- > I-). This and decreasing activity, selectivity, and halide sequence with increasing positive charge of the rod termini support the occurrence of anion-pi interactions. A strong anomalous mole fraction effect in Cl-/I- mixtures is in agreement with the existence of multiple active sites along the anion-pi slide and multi-anion hopping as a mechanism of transport. The strong inverted NDI quadruple moment found by DFT calculations is in excellent agreement with these results

Synthetic Multifunctional Pores that Open and Close in Response to Chemical Stimulation

Studies on synthetic multifunctional pores with external and internal active sites for ligand gating and noncompetitive blockage are presented, with emphasis on the contribution of external ligands to the characteristics of the pore. A comparison between different synthetic multifunctional pores reveals that the location of functional groups in rigid-rod beta-barrel pores is precisely reflected in the function: molecular recognition at the outer barrel surface results in pore opening, while molecular recognition at the inner barrel surface results in pore closing. Negligible nonspecific leakage, disappearance of pH gating, inhibition of intervesicular pore transfer, and maybe also the flickering of currents of single open pores characterize external ligands as adhesive cushions that liberate the pore from lateral pressure exerted by the surrounding membrane. Refined molecular models show good agreement with pore design and experimental facts with regard to function

Synthetic multifunctional pores that open and close in response to chemical stimulation

Studies on synthetic multifunctional pores with external and internal active sites for ligand gating and noncompetitive blockage are presented, with emphasis on the contribution of external ligands to the characteristics of pore. A comparison between different synthetic multifunctional pores reveals that the location of functional groups in rigid-rod beta-barrel pores is precisely reflected in the function: molecular recognition at the outer barrel surface results in pore opening, while molecular recognition at the inner barrel surface results in pore closing. Negligible nonspecific leakage, disappearance of pH gating, inhibition of intervesicular pore transfer, and maybe also the flickering of currents of single open pores characterize external ligands as adhesive cushions that liberate the pore from lateral pressure exerted by the surrounding membrane. Refined molecular models show good agreement with pore design and experimental facts with regard to function

Synthetic Multifunctional Pores with External and Internal Active Sites for Ligand Gating and Noncompetitive Blockage

Design, synthesis, and multifunctionality of p-octiphenyl ß-barrel pores with external LRL triads and internal HH dyads are described. Molecular recognition of anionic fullerenes > calixarenes > pyrenes by guanidinium arrays at the outer pore surface is shown to result in pore opening, whereas a-helix recognition within the topologically matching internal space is shown to result in noncompetitive pore blockage. This experimental evidence for multifunctionality is supported by comparison with pertinent control pores and blockers, by structural studies using FRET from p-octiphenyl donors in the pore to BODIPY acceptors in the bilayer, and by molecular mechanics simulations. Practical usefulness of ligand-gated synthetic multifunctional pores is exemplified with the continuous detection of chemical processes