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. Author manuscript; available in PMC: 2019 Jun 11.
Published in final edited form as: Langmuir. 2018 Jul 18;34(49):14993–14999. doi: 10.1021/acs.langmuir.8b01004

Figure 4.

Figure 4.

Stability of the stem loop is a strong function of the charge on the surface to which it is tethered. Specifically, the stability of the stem-loop decreases (e.g., the urea-melt midpoint shifts to lower denaturant concentrations) as it is attached to increasingly negatively charged surfaces (surfaces of increasingly positive pzc all held at the redox potential of methylene blue). As ionic strength increases, the DNA is stabilized on all surfaces, but the stability differences between the surfaces remains nearly constant. As derived using previously published pzc,19,22 the potentials the three surfaces adopt when, as is the case here, they are subjected to an applied potential at the redox potential of methylene blue are −50 ± 10 mV, −130 ± 50 mV, and −210 ± 10 mV for C6OH, C6OOH, and C11OH, respectively (values from refs 19,22,23).