Biological mimics

Imidazole is of particular relevance to biological mimic ligands due to the presence of histidine as a coordinating group for zinc in biological systems and has been a particular target for zinc complex formation. 

Fluorine in biological mimics Peptidyl prolyl isomerases (PPIases)... 

Interest in biological mimics probably started in the late 1800s with the discovery of cyclodextrin (CD), obtained from the starch digest of a strain of Bacillus. The realization that CDs could form host-guest complexes with a variety of small molecules, and the myriad of uses implied therein, led to extensive study in both academics and industry. 

Early work in the area of crown ether biological mimics was reported by Vogtle and coworkers (Tummler, 1977). These early compounds were made in an effort to duplicate natural ion carriers in the sense that they could complex biologically important ions for transport. The early, two-dimensional crowns (such as 5) and non-cyclic polyethers gave way to the three-dimensional ciyptands (6), which generally complexed ions more tightly but which lack the dynamics of podands, crown ethers, or lariat ethers. 

An important observation needs to be made about channel models and, indeed, model systems in general. Chemists can design molecules to have remarkable shapes and sizes. For a model system, however, it is the properties that determine whether the compound is relevant. A compound that looks like it should be a channel is, as Fitzmaurice has put it, only a long thin thing absent a demonstration of efficacy (Fitzmaurice, 2004). There is no rule that demands selectivity for the biologically relevant ions. Indeed, transport of divalent cobalt has been studied. A cobalttransporting channel is not, however, a biological mimic so far as is currently known. 

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