nn6b00393_si_001.pdf (1.55 MB)
Real-Space Evidence of Rare Guanine Tautomer Induced by Water
journal contribution
posted on 2016-02-13, 00:00 authored by Chi Zhang, Lei Xie, Yuanqi Ding, Qiang Sun, Wei XuWater
is vital for life as a solvent. Specifically, it has been
well established that DNA molecules are hydrated in vivo, and water
has been found to be responsible for the presence of some noncanonical
DNA base tautomers. Theoretical investigations have shown that the
existence of water could significantly influence the relative stability
of different DNA base tautomers, reduce the energy barrier of tautomeric
conversions, and thus promote the formation of some rare base tautomers.
In this work, we report the real-space experimental evidence of rare
base tautomers. From the high-resolution scanning tunneling microscopy
imaging, we surprisingly find the formation of the rare guanine tautomer, i.e., G/(3H,7H) form, on the Au(111) surface by delicately
introducing water into the system. The key to the formation of this
rare tautomer is proposed to be the “water bridge” that
largely reduces the energy barriers of intramolecular proton-transfer
processes as revealed by extensive density functional theory calculations.
The real-space experimental evidence and the proposed mechanism make
a step forward toward the fundamental understanding of water-assisted
base tautomerization processes.