Figure 1.

To explore the thermodynamic consequences of crowding for surface-tethered biomolecules, we have measured the folding free energy of (top) a simple DNA stem-loop attached by one terminus to a hydroxyl-terminated, six-carbon thiol-on-gold self-assembled monolayer (SAM). A redox-active methylene blue reporter on its distal terminus provides a means of monitoring the unfolding of the stem-loop using (bottom) square-wave voltammetry. Recovery of the original peak height after urea-induced unfolding and subsequent refolding illustrates the reversibility of folding under the experimental conditions we have employed.