SCANNING TUNNELING MICROSCOPE IMAGE OF THIOGUANINE MOLECULES ON AU(111) SURFACE

We have studied 6-thioguanine, a substituent of deoxyribonucleic acid (DNA) bases, adsorbed on a Au(111) surface by scanning tunneling micro scopy (STM) under ambient condition in air. Observation of the STM ima ge of the molecule suggests that thioguanine is bound to the Au substr ate through the Au-S bond formation described in STM studies of alkane thiolate molecules. Our STM images obtained under ambient condition ar e much more similar to those of a planar two-dimensional hydrogen-bond ed array of guanine molecules on a MoS2 substrate rather than those of a disordered array of guanine on a Au substrate in solution.