Structure of the Fully Modified Left-Handed Cyclohexene Nucleic Acid Sequence GTGTACAC.

CeNA oligonucleotides consist of a phosphorylated backbone where the deoxyribose sugars are replaced by cyclohexene moieties. The X-ray structure determination and analysis of a fully modified octamer sequence GTGTACAC, which is the first crystal structure of a carbocyclic-based nucleic acid, is presented. This particular sequence was built with left-handed building blocks and crystallizes as a left- handed double helix. The helix can be characterized as belonging to the (mirrored) A-type family. Crystallographic data were processed up to 1.53 Å, and the octamer sequence crystallizes in the space group R32. The sugar puckering is found to adopt the ³H2 half-chair conformation which mimics the C3′-endo conformation of the ribose sugar. The double helices stack on top of each other to form continuous helices, and static disorder is observed due to this end-to-end stacking. [ABSTRACT FROM AUTHOR]