Where is the sodium in self-assembled monolayers of single-stranded DNA?

Supratim Guha Ray, Hagai Cohen, Ron Naaman, Yitzhak Rabin

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Monolayers of single-stranded DNA (ssDNA) immobilized on surfaces form the basis of a number of important biotechnology applications, including DNA microarrays and biosensors. The organization of ssDNA as layer on a solid substrate allows one to investigate various properties of the DNA in a controlled manner and to use DNA for analytical applications as well as for exploring futuristic schemes for molecular electronics. It is commonly assumed that the adsorbed DNA layer contains some structural water and the cations. Here we show, based on XPS studies, that when monolayers of ssDNA are formed from sodium phosphate buffer and washed thoroughly, no Na+ signal is detected. A finite concentration of ions is observed when the DNA is made from a solution of Mg2+ ions, but it is still only a fifth of what it would be if all the phosphate ions were fully neutralized by the metal cations.

Original languageEnglish
Pages (from-to)17138-17139
Number of pages2
JournalJournal of the American Chemical Society
Issue number49
StatePublished - 14 Dec 2005


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