title: An investigation into the interactions between self-assembled adenine molecules and a Au(111) surface.
abstract: Two molecular phases of the DNA base adenine (A) on a Au(111) surface are observed by using STM under ultrahigh-vacuum conditions. One of these phases is reported for the first time. A systematic approach that considers all possible gas-phase two-dimensional arrangements of A molecules connected by double hydrogen bonds with each other and subsequent ab initio DFT calculations are used to characterize and identify the two phases. The influence of the gold surface on the structure of A assemblies is also discussed. DFT is found to predict a smooth corrugation potential of the gold surface that will enable A molecules to move freely across the surface at room temperature. This conclusion remains unchanged if van der Waals interaction between A and gold is also approximately taken into account. DFT calculations of the A pairs on the Au(111) surface show its negligible effect on the hydrogen bonding between the molecules. These results justify the gas-phase analysis of possible assemblies on flat metal surfaces. Nevertheless, the fact that it is not the most stable gas-phase monolayer that is actually observed on the gold surface indicates that the surface still plays a subtle role, which needs to be properly addressed.
authors.affiliation: Department of Physics, School of Physical Science and Engineering, King's College London, Strand London, UK.
authors.forename: Ross E A
authors.initials: RE
authors.lastname: Kelly
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.forename: Maya
authors.initials: M
authors.lastname: Lukas
authors.forename: Roberto
authors.initials: R
authors.lastname: Otero
authors.forename: Manuela
authors.initials: M
authors.lastname: Mura
authors.forename: Young-Joo
authors.initials: YJ
authors.lastname: Lee
authors.forename: Erik
authors.initials: E
authors.lastname: Laegsgaard
authors.forename: Ivan
authors.initials: I
authors.lastname: Stensgaard
authors.forename: Lev N
authors.initials: LN
authors.lastname: Kantorovich
authors.forename: Flemming
authors.initials: F
authors.lastname: Besenbacher
mesh_terms: D000225:Adenine / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling; D008958:Models, Molecular; D008968:Molecular Conformation; D013499:Surface Properties
chemical_list: D006046:Gold; D000225:Adenine