A method for adsorbing nucleic acids to a surface of a gold substrate for analyzing the structure of the nucleic acid includes the steps of thiolating the nucleic acid by substituting at least one non-bridging internucleotide oxygen of each phosphodiester moiety with sulfur, depositing the thiolated nucleic acid on the gold surface, and subjecting the nucleic acid to analysis for determining the atomic or molecular structure thereof. The gold surface is prepared by subjecting a gold single crystal to mechanical polishing, electropolishing, cleaning by cycles of Ar.sup.+ sputtering and annealing under vacuum until no contamination is detected by Auger electron spectroscopy, and flame annealing and quenching in methanol. Gold films deposited on atomically flat substrates, such as mica, can also be used. The thiolated DNA is deposited on the gold surface for a sufficient time for covalent bonds to form between the sulfur and the gold. Scanning tunneling microscopy, atomic force microscopy, angle-dependent x-ray photoelectron spectroscopy, and Auger electron spectroscopy are used to analyze the nucleic acid structure.