Multipoint hydrogen bonding

Figure 6.7 Illustration of multipoint hydrogen bonding based self-assembly (a) hydrogen bond formation between barbituric acid functionalized gold nanoparticles and Hamilton receptor functionalized block copolymers and (b) selective deposition of nanoparticles on a microphase-separated block copolymer film. Reprinted with permission fi om Binder et al. (2005). Copyright 2005 American Chemical Society.

Scheme 14 Presumptive multipoint hydrogen bonding between Ur6IN and DAP systems.

Protein Binding—Tannins, as the name implies, characteristically form complexes with proteins based on multipoint hydrogen bonding, and this feature can be used to detect and remove tannins from crude extracts. A visible protein-tannin precipitate should be formed on addition of the tannin-containing extract to a relatively concentrated (approx 5%) solution of bovine serum albumin (BSA). The amount of BSA either remaining in solution or in the precipitate can be analyzed by various protein determination assays. 

Adsorbent Binding—In the same way that tannins bind to proteins through multipoint hydrogen bonding, so do they also bind to a number of other polymeric materials. These include the adsorbents commonly used to remove tannins... 

This complex polyhedral connectivity generates channels parallel to the ac plane occupied by the diammonium cations and water molecules of crystal-hzation. The aqua hgands of one vanadium site also project into these channels. The cations are locked into position by strong multipoint hydrogen bonding to oxygen atoms of the framework, as indicated by N O distances in the 2.75-2.95-A range. 

Figure 13 Tetrameric capsule showing binding of a diketone that makes multipoint hydrogen bonding with the top and bottom of the capsule.

The two oxovanadium phosphate phases and the oxovanadium phosphite material whose syntheses are described contain alkyldiammonium cations whose presence is essential to the isolation of the products. The structures of these materials, which are represented schematically in Figs. 1-3, reveal the importance of hydrophobic/hydrophilic interactions and multipoint hydrogen bonding. 

The present review is intended to provide some new and novel aspects of the supramolecular chemistry. The contents are based on the author s own work on multipoint hydrogen-bonding in apolar organic solutions. Molecular recognition of polar compounds in the solid states and in aqueous media are also introduced in view of potential application of supramolecular chemistry to the material science and technology as well as the life science and technology. 

Multipoint hydrogen-bonding is a nature s device for the maintenance of structures and functions of informational biopolymers such as nucleic acids, proteins, and oligo- and polysaccharides. Molecular recognition based on such interactions is still in an early stage, but there have eady been accumulated many good examples that convince one of its potential utilities in modem chemical science. 

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