标题：Platform- and label-free detection of lead ions in environmental and laboratory samples using G-quadraplex probes by circular dichroism spectroscopy
其他标题：Platform- and label-free detection of lead ions in environmental and laboratory samples using G-quadraplex probes by circular dichroism spectroscopy
摘要：Guanine-rich quadruplex (G-QD) are formed by conversion of nucleotides with specific sequences by stabilization of positively charged K or Na . These G-QD structures differentially absorb two-directional (right- and left-handed) circularly polarized light, which can discriminate the parallel or anti-parallel structures of G-QDs. In this study, G-QDs stabilized by Pb2 were analyzed by a circular dichroism (CD) spectroscopy to determine Pb2 concentration in water samples. Thrombin aptamer (TBA), PS2.M, human telomeric DNA (HTG), AGRO 100, and telomeric related sequence (T2) were studied to verify their applicability as probes for platform- and label-free detection of Pb2 in environmental as well as laboratory samples. Among these nucleotides, TBA and PS2.M exhibited higher binding constants for Pb2 , 1.20–2.04 × 106/M at and 4.58 × 104–1.09 × 105/M at 100 micromolar and 100 mM K concentration, respectively. They also exhibited excellent selectivity for Pb2 than for Al3 , Cu2 , Ni2 , Fe3 , Co2 , and Cr2 . When Pb2 was spiked into an effluent sample from a wastewater treatment plant (WWTP), its existence was detected by CD spectroscopy following a simple addition of TBA or PS2.M. By the addition of TBA and PS2.M, the Pb2 signals were observed in effluent samples over 0.5 micromolar (100 ppb) concentration. Furthermore, PS2.M caused a Pb2 -specific absorption band in the effluent sample without spiking of Pb2 , and could be induced to G-QD structure by the background Pb2 concentration in the effluent, 0.159 micromolar concentration (3.30 ppb). Taken together, we propose that TBA and PS2.M are applicable as platform- and label-free detection probes for monitoring Pb2 in environmental samples such as discharged effluent from local WWTPs, using CD spectroscopy.
