Quantifying the Temperature Dependence of Glycine—Betaine RNA Duplex Destabilization

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• 作者：Jeffrey J. Schwinefus ; Ryan J. Menssen ; James M. Kohler ; Elliot C. Schmidt ; Alexandra L. Thomas
• 刊名：Biochemistry
• 出版年：2013
• 出版时间：December 23, 2013
• 年：2013
• 卷：52
• 期：51
• 页码：9339-9346
• 全文大小：328K
• ISSN：1520-4995

文摘

Glycine鈥揵etaine (GB) stabilizes folded protein structure because of its unfavorable thermodynamic interactions with amide oxygen and aliphatic carbon surface area exposed during protein unfolding. However, GB can attenuate nucleic acid secondary structure stability, although its mechanism of destabilization is not currently understood. Here we quantify GB interactions with the surface area exposed during thermal denaturation of nine RNA dodecamer duplexes with guanine鈥揷ytosine (GC) contents of 17鈥?00%. Hyperchromicity values indicate increasing GB molality attenuates stacking. GB destabilizes higher-GC-content RNA duplexes to a greater extent than it does low-GC-content duplexes due to greater accumulation at the surface area exposed during unfolding. The accumulation is very sensitive to temperature and displays characteristic entropy鈥揺nthalpy compensation. Since the entropic contribution to the m-value (used to quantify GB interaction with the RNA solvent-accessible surface area exposed during denaturation) is more dependent on temperature than is the enthalpic contribution, higher-GC-content duplexes with their larger transition temperatures are destabilized to a greater extent than low-GC-content duplexes. The concentration of GB at the RNA surface area exposed during unfolding relative to bulk was quantified using the solute-partitioning model. Temperature correction predicts a GB concentration at 25 掳C to be nearly independent of GC content, indicating that GB destabilizes all sequences equally at this temperature.