Coadsorption of guanine and cytosine on graphite: Ordered structure based on GC pairing

Nanostructures formed by coadsorption of the complementary DNA bases guanine ( G) and cytosine ( C) at a graphite surface in 1-octanol solvent were investigated by in situ scanning tunneling microscopy. The high-resolution observations showed for the first time a well-ordered coadsorption structure, attributed to rows formed from Watson-Crick G-C pairs, which was distinctly different from the structures observed for the individual G/C components. The observed coadsorption structure has been modeled by self-consistent charge density-functional-based tight-binding (SCC-DFTB) calculations, providing information on the intermolecular interactions underlying its formation.