Nucleotides are constituents of nucleic acids and they have a variety of functions in cellular metabolism. Synthetic receptors and sensors are required to reveal the role of nucleotides in living organisms and mechanisms of signal transduction events. In recent years, a large number of nucleotide‐selective synthetic receptors have been devised, which utilize different molecular designs and sensing mechanisms. This Minireview presents recent progress in the design of synthetic molecular receptors for selective recognition of nucleotides in aqueous solution. The binding properties of receptors and the origins of their selectivity for a particular nucleotide are discussed.
Pyrene-based cyclophanes have been synthesized with the aim to realize ab ellows-type sensing mechanism for the ratiometric detection of nucleotide concentrations in ab uffered aqueous solution. The sensing mechanism involves the encapsulationo fan ucleobase between two pyrene rings,w hich affects the monomer-excimer equilibrium of the receptori nt he excited state. The nature of the spacer and its connection pattern to pyrene rings have been varied to achieve high selectivity for ATP. The 1,8-substituted pyrene-basedc yclophane with the 2,2'-diaminodiethylamine spacer demonstrates the best selectivity for ATPs howing a 50-fold increase in the monomer-excimer emission ratio upon saturation with the nucleotide. The receptor can detect ATPw ithin the biological concentrations range over a wide pH range. NMR and spectroscopic studies have revealed the importance of hydrogen bonding and stacking interactions for achievingarequired receptors electivity.T he probe has been successfully applied for the real-time monitoring of creatine kinase activity.
A receptor containing amidopyrrole binding subunits and free amino groups, conjugated to a naphthalimide dye, has been designed and synthesized. The intrinsic selectivity of the binding motif for phosphate present in DMSO completely disappears in 10 % DMSO aqueous buffer at pH 3.6, at which the receptor is protonated. The electrostatic interactions between the receptor and an anion start to dominate, thus leading to selectivity for sulfate. The ability of the HSO anion to transfer the proton to the amino group during the recognition event suppresses the photoinduced electron transfer (PET) on the dye, resulting in a selective turn-on fluorescent response. The choice of pH of the solution for sensing is dictated by the pK value of the dye.
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