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  • Title: Is the G-quadruplex an effective nanoconductor for ions?
    Author: Ngo VA, Di Felice R, Haas S.
    Journal: J Phys Chem B; 2014 Jan 30; 118(4):864-72. PubMed ID: 24397412.
    Abstract:
    We use a stepwise pulling protocol in molecular dynamics simulations to identify how a G-quadruplex selects and conducts Na(+), K(+), and NH4(+) 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(+) > Na(+) > NH4(+). This order implies that K(+) optimally fits the channel. However, the features of the free-energy profiles indicate that the channel conducts Na(+) 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.
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