A Dynamic Combinatorial Approach for Identifying Side Groups that Stabilize DNA-Templated Supramolecular Self-Assemblies

DNA-templated self-assembly is an emerging strategy for generating functional supramolecular systems, which requires the identification of potent multi-point binding ligands. In this line, we recently showed that bis-functionalized guanidinium compounds can interact with ssDNA and generate a supramolecular complex through the recognition of the phosphodiester backbone of DNA. In order to probe the importance of secondary interactions and to identify side groups that stabilize these DNA-templated self-assemblies, we report herein the implementation of a dynamic combinatorial approach. We used an in situ fragment assembly process based on reductive amination and tested various side groups, including amino acids. The results reveal that aromatic and cationic side groups participate in secondary supramolecular interactions that stabilize the complexes formed with ssDNA.     

Synthesis and property of hydrogel membranes consisting of fumaramate with phosphorylcholine group

Fumaramate bearing a phosphoryl choline group, isopropyl‐2‐[2′‐(trimethylammonium) ethyl phosphoryl] ethyl fumaramate (IPTPFA), was radically copolymerized with 2‐hydroxyethylmethacrylate (HEMA) in the presence of various crosslinking agents, water, and 2,2′‐azobis(isobutyronitrile) to obtain hydrogel membranes. The obtained hydrogel membranes adsorbed bovine serum albumin (BSA) much less than those of poly(HEMA), and the values of water content (H) were higher than those of poly(HEMA). The values of tensile strength and tensile elongation of the hydrogel were 68.4 g/mm² and 239%, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2552–2557, 2004     

NMR Studies on Li+, Na+ and K+ Complexes of Orthoester Cryptand o-Me2-1.1.1

Cryptands, a class of three-dimensional macrobicyclic hosts ideally suited for accommodating small guest ions, have played an important role in the early development of supramolecular chemistry. In contrast to related two-dimensional crown ethers, cryptands have so far only found limited applications, owing in large part to their relatively inefficient multistep synthesis. We have recently described a convenient one-pot, template synthesis of cryptands based on O,O,O-orthoesters acting as bridgeheads. Here we report variable-temperature, ¹H-1D EXSY and titration NMR studies on lithium, sodium, and potassium complexes of one such cryptand (o-Me₂-1.1.1). Our results indicate that lithium and sodium ions fit into the central cavity of the cryptand, resulting in a comparably high binding affinity and slow exchange with the bulk. The potassium ion binds instead in an exo fashion, resulting in relatively weak binding, associated with fast exchange kinetics. Collectively, these results indicate that orthoester cryptands such as o-Me₂-1.1.1 exhibit thermodynamic and kinetic properties in between those typically found for classical crown ethers and cryptands and that future efforts should be directed towards increasing the binding constants.