Peptoids, N-substituted glycine oligomers, can adopt stable three-dimensional structures and have found diverse application as peptide surrogates and as nanomaterials. In this report, we have expanded peptoid function to include pH sensing by coupling pH-induced peptoid conformational changes with fluorescence intensity changes. We report two new peptoids (2 and 3) that comprise carboxylic-acid functionalized side chains and undergo conformational rearrangement in response to pH. Peptoids 2 and 3 are also labeled at one side-chain with an environmentally sensitive fluorophore, 4-N,N-dimethylamino-1,8-naphthalimide (4DMN). The fluorescence intensity of 2 varies 24-fold over the pH range studied. These spectroscopic properties make 2 a sensitive, biocompatible pH sensor.
Keywords: conformational rearrangement; environmentally sensitive fluorophore; peptidomimetic; peptoid oligomer.
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