Base-dependent competitive adsorption of single-stranded DNA on gold.

We characterize the room-temperature adsorption of single-stranded DNA homo-oligonucleotides from solution onto polycrystalline Au films, including competitive adsorption between all possible pairs of unmodified oligomers. Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopy analysis of the resulting films shows that oligonucleotides adsorb with a strongly base-dependent affinity, adenine (A) > cytosine (C) >/= guanine (G) > thymine (T). In competitive adsorption experiments on Au, oligo(dA) strongly dominates over the other oligonucleotides. The relative adsorption affinity of oligo(dA) is so great that it competes effectively against adsorption of thiolated oligomers and even causes hybridized oligo(dA).oligo(dT) duplexes to denature in the presence of Au.