Is the
G‑Quadruplex an Effective Nanoconductor
for Ions?
- Publication date
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Abstract
We use a stepwise pulling protocol
in molecular dynamics simulations
to identify how a G-quadruplex selects and conducts Na<sup>+</sup>, K<sup>+</sup>, and NH<sub>4</sub><sup>+</sup> ions. By estimating
the minimum free-energy changes of the ions along the central channel
via Jarzynski’s equality, we find that the G-quadruplex selectively
binds the ionic species in the following order: K<sup>+</sup> >
Na<sup>+</sup> > NH<sub>4</sub><sup>+</sup>. This order implies
that K<sup>+</sup> optimally fits the channel. However, the features
of the
free-energy profiles indicate that the channel conducts Na<sup>+</sup> best. These findings are in fair agreement with experiments on G-quadruplexes
and reveal a profoundly different behavior from the prototype potassium-ion
channel KcsA, which selects and conducts the same ionic species. We
further show that the channel can also conduct a single file of water
molecules and deform to leak water molecules. We propose a range for
the conductance of the G-quadruplex