Functionalizing Designer DNA Crystals with a Triple‐Helical Veneer

DNA is a very useful molecule for the programmed self‐assembly of 2D and 3D nanoscale objects. 1 The design of these structures exploits Watson–Crick hybridization and strand exchange to stitch linear duplexes into finite assemblies. 2 – 4 The dimensions of these complexes can be increased by over five orders of magnitude through self‐assembly of cohesive single‐stranded segments (sticky ends). 5 , 6 Methods that exploit the sequence addressability of DNA nanostructures will enable the programmable positioning of components in 2D and 3D space, offering applications such as the organization of nanoelectronics, 7 the direction of biological cascades, 8 and the structure determination of periodically positioned molecules by X‐ray diffraction. 9 To this end we present a macroscopic 3D crystal based on the 3‐fold rotationally symmetric tensegrity triangle 3 , 6 that can be functionalized by a triplex‐forming oligonucleotide on each of its helical edges.     

Controlled Stability of the Triple‐Stranded Helical Structure of a β‐1,3‐Glucan with a Chromophoric Aromatic Moiety at a Peripheral Position

We synthesized a semiartificial β‐1,3‐glucan, curdlan with dialkylaniline groups (CUR‐DA), that bears chromophoric aromatic groups at its peripheral positions. Spectroscopic studies as well as microscopic observations indicate that CUR‐DA adopts a triple‐stranded helical structure in water‐ or methanol‐rich solutions of dimethyl sulfoxide (DMSO). This triple‐stranded helical structure exhibits high thermal stability and resistance to base, attributes that are similar to those of the triple‐stranded helical structure of native β‐1,3‐glucans such as schizophyllan. Moreover, we found that the stability of the triple‐stranded helical structure can be easily modulated by solvent composition and metal‐ion (Zn²⁺) binding. As β‐1,3‐glucan polysaccharides are known to serve as “polymeric” hosts, including certain DNA molecules, carbon nanotubes, and conjugated polymers, and complexation occurs only with the single‐stranded structure, this information is very useful for the creation of these attractive polymeric composites, the controlled release of DNA, and so on.     

Supramolecular Assembly of Double‐Stranded Chains,Helical Chains and Catenane‐like Layers with Flexible Ligands

Four new transition metal coordination polymers, [Co(bpndc)(phen)(H₂O)]_n ( 1 ), [Co₃(bpndc)₃(2,2′‐bpy)₂]_n·0.5n(i‐C₃H₇OH) ( 2 ), and [M(bpndc)(2,2′‐bpy)₂]_n (M = Zn, 3 ; Cu, 4 ; H₂bpndc = benzophenone ‐4,4′‐dicarboxylic acid; phen = 1,10‐phenanthroline; 2,2′‐bpy = 2,2′‐bipyridine) have been synthesized by the hydrothermal reactions and characterized by single crystal X‐ray diffraction, elemental analysis, and IR spectrum. Because of the introduction of different terminal auxiliary ligands, bpndc ligands in complexes 1 and 2 adopt different coordination modes. In complex 1 , bpndc ligands act as tridentate ligand and bridge Co^II ions into 1D double‐stranded chains; while complex 2 possesses 2D (4,4) grids, where bpndc ligands adopt tetradente and pentadentate modes. Two such grids interpenetrate to form a novel catenane‐like layer. Complexes 3 and 4 are isostructural. Bpndc ligands adopt tetradentate mode and bridge metal ions forming 1D helical chains.     

Aurovertin‐Type Polyketides from Calcarisporium arbuscula with Potent Cytotoxic Activities against Triple‐Negative Breast Cancer

Two new polyene polyketides, namely aurovertins T and U ( 1 and 2 ), were isolated from Calcarisporium arbuscula, together with aurovertins B ( 3 ), D and E ( 4 and 5 ), and M ( 6 ). The structures were elucidated by extensive spectroscopic methods (especially 2D‐NMR techniques). The cytotoxic activities of all isolates against human triple‐negative breast cancer cell line (MDA‐MB‐231) were evaluated. As a result, compounds 3 , 4 , and 6 exhibited more potent cytotoxic activities against MDA‐MB‐231 cell line than the positive control taxol. Also, discussion about the relationships between structure and activity of these aurovertins was presented.     

Surface‐Modifiable Free‐Floating Films Formed by Multiway Connection of Collagen‐Like Triple‐Helical Peptides

Square‐millimeter‐sized free‐floating translucent films are formed in physiological buffer by multiway connections between biotinylated collagen‐like triple‐helical peptides and avidin. Although the compositions of the films are almost constant, regardless of the ratios of the components loaded, their thicknesses can be controlled by the concentrations of the components. The film surfaces can be further modified by taking advantage of exposed biotin (or avidin) functionalities. The self‐assembled films could serve as novel materials in biomedical and biosensing applications.     

Targeting of Single‐Stranded Oligonucleotides through Metal‐Induced Cyclization of Short Complementary Strands

A new strategy to cyclize short synthetic oligonucleotides on DNA or RNA target strands is described. The approach is based on metal‐templated cyclization of short synthetic oligonucleotides conjugated with two chelating 2,2′ : 6′,2′′‐terpyridine (Tpy) moieties at their 3′‐ and 5′‐ends. Cyclization after metal addition (Zn²⁺, Fe²⁺) was demonstrated by means of thermal‐denaturation experiments, MALDI‐Q‐TOF‐MS, and gel electrophoresis (PAGE). 1D‐ and 2D‐NMR Experiments were performed to analyze the association of complementary strands after metal‐mediated cyclization. Our protocol allows the efficient circularization of synthetic oligonucleotides. Thereby, the hybridization on a complementary strand was more efficient with an RNA target strand and a 2′‐O‐methylated circularized oligomer.     

Neue molekulare Indium‐Zinn‐Sauerstoff‐ und Indium‐Zinn‐Natrium‐Sauerstoff‐Chlor‐Cluster

Abstract. The five‐membered heteroelement cluster THF · Cl₂In(O^tBu)₃Sn reacts with the sodium stannate [Na(O^tBu)₃Sn]₂ to produce either the new oxo‐centered alkoxo cluster ClInO[Sn(O^tBu)₂]₃ ( 1 ) (in low yield) or the heteroleptic alkoxo cluster Sn(O^tBu)₃InCl₃Na[Sn(O^tBu)₂]₂ ( 2 ). X‐ray diffraction analyses reveal that in compound 1 the polycyclic entity is made of three tin atoms which together with a central oxygen atom form a trigonal, almost planar triangle, perpendicular to which a further indium atom is connected through the oxygen atom. The metal atoms thus are arranged in a Sn₃In pyramid, the edges of which are all saturated by bridging tert‐butoxy groups. The indium atom has a further chloride ligand. Compound 2 has two trigonal bipyramids as building blocks which are fused together at a six coordinate indium atom. One of the bipyramids is of the type SnO₃In with tert‐butyl groups on the oxygen atoms, while the other has the composition InCl₃Na with chlorine atoms connecting the two metals. The sodium atom in 2 has further contacts to two plus one alkoxide groups which are part of a[Sn(O^tBu)₂]₂ dimer disposing of a Sn₂O₂ central cycle. The hetero element cluster in 2 thus combines three closed entities and its skeleton SnO₃InCl₃NaO₂Sn₂O₂ consists of three different metallic and two different non‐metallic elements.     

金属配合物和原子簇化合物的电致化学发光及其应用

评述了金属配合物和原子簇化合物电致化学发光研究及应用的现状与进展,引用文献５０篇。     

Alpha‐Helical Fragaceatoxin C Nanopore Engineered for Double‐Stranded and Single‐Stranded Nucleic Acid Analysis

Nanopores are used in single‐molecule DNA analysis and sequencing. Herein, we show that Fragaceatoxin C (FraC), an α‐helical pore‐forming toxin from an actinoporin protein family, can be reconstituted in sphingomyelin‐free standard planar lipid bilayers. We engineered FraC for DNA analysis and show that the funnel‐shaped geometry allows tight wrapping around single‐stranded DNA (ssDNA), resolving between homopolymeric C, T, and A polynucleotide stretches. Remarkably, despite the 1.2 nm internal constriction of FraC, double‐stranded DNA (dsDNA) can translocate through the nanopore at high applied potentials, presumably through the deformation of the α‐helical transmembrane region of the pore. Therefore, FraC nanopores might be used in DNA sequencing and dsDNA analysis.