Yang Ying-Wei, Zhang Su, McCullum Elizabeth O, Chaput John C
The Center for BioOptical Nanotechnology, The Biodesign Institute, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
J Mol Evol. 2007 Sep;65(3):289-95. doi: 10.1007/s00239-007-9017-9. Epub 2007 Sep 9.
Systematic investigation into the chemical etiology of ribose has led to the discovery of glycerol nucleic acid (GNA) and threose nucleic acid (TNA) as possible progenitor candidates of RNA in the origins of life. Coupled with their chemical simplicity, polymers for both systems are capable of forming stable Watson-Crick antiparallel duplex structures with themselves and RNA, thereby providing a mechanism for the transfer of genetic information between successive genetic systems. Investigation into whether both polymers arose independently or descended from a common evolutionary pathway would provide additional constraints on models that describe the emergence of a hypothetical RNA world. Here we show by thermal denaturation that complementary GNA and TNA mixed sequence polymers are unable, even after prolonged incubation times, to adopt stable helical structures by intersystem cross-pairing. This experimental observation suggests that GNA and TNA, whose structures derive from one another, were not consecutive polymers in the same evolutionary pathway to RNA.
对核糖化学起源的系统研究导致发现了甘油核酸（GNA）和苏糖核酸（TNA），它们可能是生命起源中RNA的祖先候选者。这两个系统的聚合物除了化学结构简单外，还能够与自身以及RNA形成稳定的沃森-克里克反平行双链结构，从而为连续遗传系统之间的遗传信息传递提供了一种机制。研究这两种聚合物是独立产生还是源自共同的进化途径，将为描述假设的RNA世界出现的模型提供更多限制。在这里，我们通过热变性表明，互补的GNA和TNA混合序列聚合物即使经过长时间孵育，也无法通过系统间交叉配对形成稳定的螺旋结构。这一实验观察结果表明，结构相互衍生的GNA和TNA并非通往RNA的同一进化途径中的连续聚合物。
