3 years ago

Linking pH, Temperature, and K+ Concentration for DNA i-Motif Formation

Linking pH, Temperature, and K+ Concentration for DNA i-Motif Formation
Tra Nguyen, Claudette Fraire, Richard D. Sheardy
The conformation a particular DNA segment assumes depends upon its sequence context and the environment under which it is prepared. To complement our findings with G-rich sequences related to the human telomere, we have been investigating the pH induced transition from single strand to i-motif for sequences related to the human telomere C-rich strand. We have carried out titrations of (CCCTAA)4 from pH 7.0 to pH 5.0 at temperatures ranging from 15 to 45 °C at 115 mM K+ and at K+ concentrations ranging from 15 to 215 mM at 25 °C. Circular dichroism (CD) spectra were determined to monitor the transition. The pH at the midpoint of the proton induced transition, pHmp, is dependent upon both temperature and [K+]. Wyman-type plots of log K vs pH yielded linear correlations and the slopes of those lines, ΔQ, were also linearly dependent on [K+] and T. For these studies, ΔQ represents the minimum number of protons that must be added to the oligomer to induce the initial folding. These results are consistent with Le Chatelier’s principle. Optical melting studies were also carried out for (CCCTAA)4 at pH 5.0 and [K+] ranging from 15 to 315 mM. Linear correlations between the temperature at the midpoint of the transition, Tm, and log [K+] allowed determination of the differential ion binding term, ΔnK+. These linkages between pH, temperature, and [K+] can be utilized to design i-motif forming DNA oligomers with highly tunable properties.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcb.7b06317

DOI: 10.1021/acs.jpcb.7b06317

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.