A cyclic tetrapeptide paired with six commercially available indicators provides a chemosensing array able to classify biological phosphate derivatives.

The head-to-tail cyclic hexapeptide, [cyclo(Val-Thr)3], was found to bind to a range of anions in DMSO-d6 with higher affinity for tetrahedral oxo-anions than halides.1 H NMR spectroscopy indicated that anion binding results in an overall change in peptide conformation with binding of both sulfate and selenate leading to similar peptide conformations. In the more competitive solvent mixture of 2:8 v/v H2O/DMSO-d6 this cyclic peptide displayed five-fold stronger binding to sulfate than to selenate.

Chemosensors that can discriminate between nucleotide phosphates are difficult to prepare. Here we describe the use of a sensing array comprising metal complexes of bis(dipicolylamino)-functionalised linear peptide based fluorescent sensors for the discrimination of nucleotide phosphates. We demonstrate that through the rational incorporation of additional sensor elements the discriminatory power of the array can be improved. An array incorporating two peptides in combination with four metal ions was able to successfully discriminate all triphosphates and diphosphates tested. When monophosphates were included in the analysis, 91 % of the analytes (blank, AMP, ADP, ATP, CMP, CDP, CTP, GMP, GDP, GTP, UMP, UDP and UTP) could be correctly classified, with all classification errors related to monophosphates.

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