title: Real-Space Evidence of Rare Guanine Tautomer Induced by Water.
abstract: Water 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.
authors.affiliation: Tongji-Aarhus Joint Research Center for Nanostructures and Functional Nanomaterials, College of Materials Science and Engineering, Tongji University , Caoan Road 4800, Shanghai 201804, People's Republic of China.
authors.forename: Chi
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Tongji-Aarhus Joint Research Center for Nanostructures and Functional Nanomaterials, College of Materials Science and Engineering, Tongji University , Caoan Road 4800, Shanghai 201804, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Xie
authors.affiliation: Tongji-Aarhus Joint Research Center for Nanostructures and Functional Nanomaterials, College of Materials Science and Engineering, Tongji University , Caoan Road 4800, Shanghai 201804, People's Republic of China.
authors.forename: Yuanqi
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Tongji-Aarhus Joint Research Center for Nanostructures and Functional Nanomaterials, College of Materials Science and Engineering, Tongji University , Caoan Road 4800, Shanghai 201804, People's Republic of China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Sun
authors.affiliation: Tongji-Aarhus Joint Research Center for Nanostructures and Functional Nanomaterials, College of Materials Science and Engineering, Tongji University , Caoan Road 4800, Shanghai 201804, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
mesh_terms: D004247:DNA / Q000737:chemistry; D006147:Guanine / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling; D008958:Models, Molecular; D011522:Protons; D013237:Stereoisomerism; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D011522:Protons; D014867:Water; D006147:Guanine; D004247:DNA
keywords: density functional theory; guanine; scanning tunneling microscopy; surface chemistry; tautomerization