Tuning the sensing range of potassium ions by changing the loop size of G-quadruplex sensors
Here, the effect of loop size in a series of G-quadruplex ((G3T2A)3G3, (G3T2)3G3 and (G3T)3G3) sensors on sensing ability for potassium ions (K+) was evaluated. Fluorescence spectroscopy, mass spectrometry, circular dichroism and isothermal titration calorimetry were applied to investigate their different performances. The results demonstrated that the saturation concentration and the response range of K+ changed to higher concentration as the loop size of the G-quadruplex sensor increased. The association constants decreased along with the increase of loop size, hence more potassium ions were needed for the equilibrium which agreed with their different sensing ranges. In brief, varying loop sizes of the G-quadruplex can efficiently tune the stability of the G-quadruplex and the sensing range of potassium ions. This may guide the design of a new G-quadruplex sensor.