Department of Biotechnology, BJM School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India.
Nucleic Acids Res. 2018 May 18;46(9):4344-4353. doi: 10.1093/nar/gky253.
The functional B-conformation of DNA succumbs to the A-form at low water activity. Methods for room temperature DNA storage that rely upon 'anhydrobiosis', thus, often encounter the loss of DNA activity due to the B→A-DNA transition. Here, we show that ionic liquids, an emerging class of green solvents, can induce conformational transitions in DNA and even rescue the dehydrated DNA in the functional B-form. CD spectroscopic analyses not only reveal rapid transition of A-DNA in 78% ethanol medium to B-conformation in presence of ILs, but also the high resistance of IL-bound B-form to transit to A-DNA under dehydration. Molecular dynamics simulations show the unique ability of ILs to disrupt Na+ ion condensation and form 'IL spine' in DNA minor groove to drive the A→B transition. Implications of these findings range from the plausible use of ILs as novel anhydrobiotic DNA storage medium to a switch for modulating DNA conformational transitions.
在低水活度下，DNA 的功能 B 构象会向 A 构象转变。因此，依靠“脱水休眠”来实现室温下 DNA 存储的方法，往往会因 B→A-DNA 转变而导致 DNA 活性丧失。在这里，我们表明，离子液体作为一类新兴的绿色溶剂，可以诱导 DNA 发生构象转变，甚至可以挽救脱水状态下具有功能的 B 构象的 DNA。圆二色光谱分析不仅揭示了在 78%乙醇介质中，A-DNA 在离子液体存在下迅速转变为 B 构象，而且还表明 IL 结合的 B 构象在脱水时对转变为 A-DNA 的高抵抗力。分子动力学模拟表明，离子液体具有独特的能力，可以破坏 Na+离子的凝聚，并在 DNA 小沟中形成“离子液脊椎”，从而驱动 A→B 转变。这些发现的意义不仅在于可能将离子液体用作新型脱水休眠 DNA 存储介质，还在于可以作为调节 DNA 构象转变的开关。
