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. Author manuscript; available in PMC: 2013 Dec 17.
Published in final edited form as: J Am Chem Soc. 2012 Jan 17;134(4):10.1021/ja208436p. doi: 10.1021/ja208436p

Figure 2.

Figure 2

We have employed urea-melts38,39 to determine the folding free energies of a DNA stem loop both in solution (using circular dichroism spectroscopy) and when attached to a gold surface. (Left) We have monitored the latter by measuring electron transfer from a redox tag (methylene blue) on the distal terminus of our stem-loop constructs. Specifically, we used square-wave voltammetry, which is sensitive to the increase in electron transfer efficiency that occurs when the redox tag approaches the surface. (Right) At low ionic strength the stem-loop is more stable in solution than on the surface. At higher ionic strength, conditions under which both solution-phase and surface-attached stem loops are more stable, this trend is reversed.