Recognition and detection of orthophosphate

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Selective recognition of anions by artificial receptors is still a great challenge in chemistry. Although there have been a large number of receptors developed that bind a certain anion selectively, almost all of them operate in organic solvents. Real applications require binding in an aqueous solution, similar to what natural proteins do. To bind anions in water is much more difficult than cations because anions have various geometries, exist in different protonation states, and possess much lower surface-charge densities as compared to isoelectronic cations. In our project, we focus on recognition and sensing of orthophosphate primarily because phosphates are an essential part of nature and living organisms. Recent prognoses predict dramatic decrease and even exhausting of phosphor-containing mineral resources during the next ca. 40 years. Thus, understanding the principles how to bind and detect orthophosphate in water is of great fundamental and technological significance. To face this challenge we are developing a strategy how to design highly selective receptors that bind orthophosphate in water. The strategy involves 1) combination of binding sites that provide simultaneously different non-covalent interactions with a guest, and 2) arrangement of these binding sites in a molecule to provide best fit between a host and a guest. Last year we have designed an artificial receptor for orthophosphate that shows unprecedented selectivity for orthophosphate in aqueous buffer - methanol mixtures. Starting from this preliminary work we plan 1) to synthesize the receptor with 100% solubility in water by introduction of water-solubilizing groups and 2) produce cyclic derivatives in order to improve overall binding properties of the receptors. In the other part of the project, we suggest a method how to functionalize basic structure of receptors to obtain turn-on fluorescent probes for orthophosphate.