Toward a Designed, Functioning Genetic System with Expanded-Size Base Pairs: Solution Structure of the Eight-Base xDNA Double Helix
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- 作者：Stephen R. Lynch ; Haibo Liu ; Jianmin Gao ; Eric T. Kool
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：November 15, 2006
- 年：2006
- 卷：128
- 期：45
- 页码：14704 - 14711
- 全文大小：665K
- 年卷期：v.128,no.45(November 15, 2006)
- ISSN：1520-5126
文摘
We describe the NMR-derived solution structure of the double-helical form of a designed eight-base genetic pairing system, termed xDNA. The benzo-homologous xDNA design contains base pairs thatare wider than natural DNA pairs by ca. 2.4 Å (the width of a benzene ring). The eight component basesof this xDNA helix are A, C, G, T, xA, xT, xC, and xG. The structure was solved in aqueous buffer using1D and 2D NMR methods combined with restrained molecular dynamics. The data show that the decamerduplex is right-handed and antiparallel, and hydrogen-bonded in a way analogous to that of Watson-CrickDNA. The sugar-phosphate backbone adopts a regular conformation similar to that of B-form DNA, withsmall dihedral adjustments due to the larger circumference of the helix. The grooves are much wider andmore shallow than those of B-form DNA, and the helix turn is slower, with ca. 12 base pairs per 360
mages/entities/deg.gif"> turn.There is an extensive intra- and interstrand base stacking surface area, providing an explanation for thegreater stability of xDNA relative to natural DNA. There is also evidence for greater motion in this structurecompared to a previous two-base-expanded helix; possible chemical and structural reasons for this arediscussed. The results confirm paired self-assembly of the designed xDNA system. This suggests thepossibility that other genetic system structures besides the natural one might be functional in encodinginformation and transferring it to new complementary strands.