A novel fluorescence sensor for uranyl ion detection based on a dansyl-modified peptide

It is of great significance to sensitively and selectively detect uranyl ion (UO 2 2+ ) in environmental and biological samples due to the high risks of UO 2 2+ to human health. However, such suitable sensors are still scarce. A novel fluorescence sensor based on a dansyl-modified peptide, Dansyl-Glu-Glu-Pro-Glu-Trp-COOH (D-P5), was efficiently synthesized by Fmoc solid phase peptide synthesis. As the first linear peptide-based fluorescence sensor for UO 2 2+ , D-P5 exhibited high selectivity and sensitivity to UO 2 2+ over 27 metal ions (UO 2 2+ , Cr 3+ , Cu 2+ , Ba 2+ , Hg 2+ , Pb 2+ , Co 2+ , Ag + , Fe 3+ , Ca 2+ , K + , Mg 2+ , Mn 2+ , Na + , Ni 2+ , Cd 2+ , Zn 2+ , Al 3+ , Dy 3+ , Er 3+ , Gd 2+ , Ho 3+ , La 3+ , Lu 3+ , Pr 3+ , Sm 3+ , Tm 3+ ) by a turn-off fluorescence response in 10 mM HEPES buffer (pH 6.3). The effects of anions such as S 2− , NO 3 – , SO 4 2− CO 3 2– , HCOO – , antioxidant ascorbic acid and 4-nitrophenyl acetate on the selectivity for UO 2 2+ detection were also studies. D-P5 sensor could be used for detecting UO 2 2+ in a good linear relationship with concentration in the range of 0–8.0 μM with a low limit of detection of 83.2 nM. Furthermore, the interaction of the sensor with UO 2 2+ was characterized by ESI-MS, IR, XPS and ITC measurements. The 1:1 binding stoichiometry between the sensor and UO 2 2+ was measured by the job’s plot and further verified by ESI-MS. The binding constant of the sensor with UO 2 2+ was calculated to be 9.8 × 10 4 M −1 by modified Benesi-Hildebrand equation. ITC results showed that the ΔH θ and ΔS θ for the interaction of D-P5 with UO 2 2+ were −(7.167 ± 1.25) kJ·mol −1 and 66.5 J·mol −1 ·K −1 , respectively. Time-resolved fluorescence spectroscopy indicated that the mechanism of fluorescence quenching of D-P5 by UO 2 2+ ion was static quenching process. In addition, this sensor displayed a good practicality for UO 2 2+ detection in lake water sample without tedious sample pretreatment.