Design, synthesis, and esterase and ion channel activity of a novel barrel-stave supramolecule with hydrophobic exterior and histidine-rich interior are reported. Voltage-dependent binding of pyrenyl-8-oxy-1,3,6-trisulfonates by histidines within p-octiphenyl beta-barrels (and not monomers) via ionic (and not hydrophobic) interactions (K(D), K(I), K(M) < 1 microM) is the basis for superb esterolytic proficiency up to (k(cat)/K(M))/k(uncat) = 9.6 x 10(5) in water and bilayer membranes. The conductance of labile ion channels formed in planar bilayer membranes is shown to be reduced by 8-hydroxypyrene-1,3,6-trisulfonate on the single- and multichannel level. [reaction: see text]

Future stochastic biomimetic chemistry within toroidal supramolecules will depend on the availability of large, transmembrane, and functionalized internal space of high stability, four properties that characterize the nanopore formed by the hexameric, cationic rigid‐rod β‐barrel (see schematic representation).

Herein, we describe the design, synthesis, structure, and function of synthetic, supramolecular b-barrel models. Assembly of octi(p-phenylene)s with complementary -Lys-Leu-Lys-NH 2 andGlu-Leu-Glu-NH 2 side chains yielded water-soluble rigid-rod b-barrels of precise length and with flexible diameter. A hydrophobic interior was evidenced by guest encapsulation. Host ± guest complexes with planarized, monomeric bcarotene within tetrameric rigid-rod bbarrels, and disc micellar astaxanthin J-aggregates surrounded by about dodecameric rigid-rod ªbicycle tiresº were prepared from mixed micelles by dialytic detergent removal. The significance of these findings for future bioorganic chemistry in confined, intratoroidal space is discussed in comparison with pertinent biological examples.

Dedicated to Prof. Wolf-Dietrich Woggon on the occasion of his 60th birthday Intermediate internal charge repulsion (ICR) is required to create synthetic pores with large, stable, transmembrane, and variably functionalized space. This conclusion is drawn from maximal transport and, in one case, catalytic activity of p-octiphenyl b-barrel pores with internal lysine, aspartate, and histidine residues around pH 7, 6, and 4.5, respectively. pK a Simulations corroborate the experimental correlation of intermediate ICR with activity and suggest that insufficient ICR causes pore −implosion× and excess ICR pore −explosion×. Esterolysis experiments support the view that the formation of stable space within multifunctional p-octiphenyl b-barrels requires more ICR in bilayer membranes than in H 2 O. Multivalency effects are thought to account for p-octiphenyl b-barrel expansion with increasing number of b-sheets, and proximity effects for unchanged pH profiles with increasing b-sheet length. Q-TOF-nano-ESI-MS barrel-denaturation experiments indicate that contributions from internal counterion effects are not negligible. The overall characteristics of p-octiphenyl bbarrel pores with internal lysine, aspartate, and histidine residues, unlike de novo −a-barrels× and similarly to certain biological channels, underscore the usefulness of rigid-rod molecules to preorganize complex multifunctional supramolecular architecture. Fig. 2. Axial view and peptide sequences of the p-octiphenyl b-barrels 1 ± 6 from Fig. 1 (8-stranded) and Fig. 3 (6stranded). One-letter abbreviations are used for amino acids (L Leu, K Lys, H His, D Asp; G ÀOCH 2 COÀ ). n number of acid/bases per supramolecule. In molecular models [9], internal distances are a % 5 ä, b % 4 ä (1: ca. 12 ä), c % 7 ä (1: ca. 23 ä), c' % 14 ä, and d % 7 ä.

The unique properties of rigid‐rod β‐barrels are used for the programmed assembly of transmembrane B‐DNA, a complex supramolecular architecture (see picture) that combines the advantages of biomembrane anisotropy with the structural variability of B‐DNA. Binding of B‐DNA in the intratoroidal space of the nanopores (KD=177 nM) was confirmed by CD spectra and the blockage of anionic dye efflux.

A considerably arduous test of a novel class of composite materials consisting of [Ru(bpy)3]2+ and TiO2 codoped zeolites Y is presented here. The [Ru(bpy)3]2+ and TiO2 codoped zeolites Y served as photocatalysts in the oxidation of the model compounds 2,4-dimethylaniline (2,4-xylidine) by H2O2 in an acidic aqueous medium. Zeolite-embedded TiO2 (nano)particles play an important role in the degradation mechanism. The first step in this complex mechanism is the photoelectron transfer from photoexcited [Ru(bpy)3]2+*, located inside the supercage of zeolite Y, to a neighboring TiO2 nanoparticle. During this electron transfer process, electron injection into the conduction band of TiO2 is achieved. The second decisive step is the reaction of this electron with H2O2, which was previously chemisorbed at the surface-region of the TiO2 nanoparticles. In this reaction, a TiO2 bound hydroxyl radical (TiO2-HO.) is created. This highly reactive intermediate initiates then the oxidation of 2,4-xylidine, which enters the zeolites framework in its protonated form (Hxyl+). The formation of 2,4-dimethylphenol as first detectable reaction product indicated that this oxidation proceeds via an electron transfer mechanism. Furthermore, [Ru(bpy)3]3+, which was created in the initiating photoelectron transfer reaction between [Ru(bpy)3]2+* and TiO2, also takes place in the oxidation of Hxyl+. [Ru(bpy)3]2+ is recycled in that reaction, which also belongs to the group of electron transfer reactions. In addition to the primary steps of this particular Advanced Oxidation Process (AOP), the dependence of the efficiency of the 2,4-xylidine degradation as a function of the [Ru(bpy)3]2+ and TiO2 loadings of the zeolite Y framework is also reported here. The quenching of [Ru(bpy)3]2+* by H2O2 as well as the photocatalytic activity of the [Ru(bpy)3]2+ and TiO2 codoped zeolite Y catalysts both follow a distinct percolation behavior in dependence of their TiO2 content.

No abstract

Herein, we describe the design, synthesis, structure, and function of synthetic, supramolecular beta-barrel models. Assembly of octi(p-phenylene)s with complementary -Lys-Leu-Lys-NH2 and Glu-Leu-Glu-NH2 side chains yielded water-soluble rigid-rod beta-barrels of precise length and with flexible diameter. A hydrophobic interior was evidenced by guest encapsulation. Host-guest complexes with planarized, monomeric beta-carotene within tetrameric rigid-rod beta-barrels, and disc micellar astaxanthin J-aggregates surrounded by about dodecameric rigid-rod "bicycle tires" were prepared from mixed micelles by dialytic detergent removal. The significance of these findings for future bioorganic chemistry in confined, intratoroidal space is discussed in comparison with pertinent biological examples.