Thiol-mediated degradation of DNA adsorbed on a colloidal gold surface

When [³²P]-labeled DNA is adsorbed on colloidal gold from a 130mmol dm^-3 solution of KH₂PO₄, it can subsequently be eluted with cold DNA without undergoing detectable degradation. Similarly, DNA can be incubated in solution in the presence or absence of colloidal gold with high concentrations of β-mercaptoethanol or hexane-1-thiol without significant degradation. However, when adsorbed DNA is eluted from gold with solutions of one of the thiols, it is recovered as a mixture of mononucleotides and short oligomers. The extent of degradation increases with increasing concentration of the thiol and with increasing elution temperature. Our results emphasize that in designing protocols involving DNA adsorbed on gold surfaces, it is important to avoid allowing the DNA to come into contact with even moderate concentrations of thiols.