Measuring the Dynamics of Cation Exchange by NMR Spectroscopy

As mentioned above, Tl can also stabilize G-quadruplex structures. The ability for Tl ions to compete with Na ions for coordination within the G-quadruplex [d(G4T4G4)]2 has been verified by solution-state H NMR. The results from these experiments were similar to the K -Na titration experiments discussed above for the same G-quadruplex. A recent solution-state NMR structure of [d(G4T4G4)]2 folded in the presence of Tl ions has also confirmed that the Tl form of this quadruplex is similar to that of the K form. The excellent NMR properties of Tl, spin 1/2 with a high natural abundance of 70% and relative sensitivity to protons of 0.13, also make ° T1 a 

5 Thermodynamics of G-Quadruplex Cation-Dependent Stability and Cation Selectivity 

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