In vitro analysis of the arabinose nanosensor FLIPara-200n. (A) In vitro Venus/enhanced yellow fluorescent protein ratio change of affinity-purified FLIPara-250n in the presence of D/L-arabinose. The binding constant Kd of the sensor is 230 ± 18 nM (derived from single-site binding isotherm fit). (B) Substrate specificity of FLIPara-250n as measured by fluorescence resonance energy transfer in the presence of various pentose ligands at three different concentrations. Data were normalized to the sensor in the absence of ligand (first bar on left). Error bars represent the standard deviation (n = 3).