posted on 2023-12-08, 09:45authored byRyan E. Johnson, Makay T. Murray, Dylan J. Roby, Lucas J. Bycraft, Zachary R. Churcher, Saanya Yadav, Philip E. Johnson, Stacey D. Wetmore, Richard A. Manderville
The ability of guanine (G)-rich DNA to bind toxic lead
(Pb2+) ions within a G-quadruplex (GQ) motif is a leading
DNA
biosensor strategy. A major analytical hurdle for GQ detection of
Pb2+ is competitive GQ templating by potassium (K+) ions. We employ the on-strand DNA synthesis of internal fluorescent
chalcone surrogates within the 15-mer thrombin binding aptamer (TBA15)
to address this challenge. Replacement of thymidine at the 3-position
(T3) within TBA15 with an indole-4-hydroxy-indanone (Ind4HI) chalcone
strongly decreases K+-GQ stability while enhancing Pb2+-GQ stability to increase Pb2+ binding specificity.
The new T3-Ind4HI probe exhibits a 15-fold increase in fluorescence
intensity upon binding of Pb2+ by the modified TBA15 and
can detect 6.4 nM Pb2+ in the presence of 10 mM K+. Thus, replacement of the T3 residue of TBA15 with the new Ind4HI
probe modulates metal ion affinity by native TBA15 to solve the analytical
challenge posed by K+ in real water samples for detecting
Pb2+ to meet regulatory guidelines by using a GQ biosensor.