A Fluorescence Sensor for Detection of Geranyl Pyrophosphate by the Chemo-Ensemble Method

Hexaamide receptor 4 and coumarin phosphate 5 form an ensemble for effective sensing of geranyl pyrophosphate (GPP). Fluorescence resonance energy transfer in the 4 + 5 ensemble diminishes when 5 is replaced by GPP. Receptor 4 binds selectively with GPP over other anions, including fatty acids. The 4-GPP complex in 1: 1 stoichiometry is inferred by NMR and fluorescence titrations. Receptor 4 contains a pseudotetrahedral cleft to accommodate GPP via Multiple hydrogen bonds, and the two aliphatic chains exert additional hydrophobic interactions.