The NMR structure of 2¢,5¢ d(GGGGCCCC) was deter-mined togain insights into the structural differences between 2¢,5¢-and 3¢,5¢-linked DNA duplexes that may be relevant in elucidating nature’s choice of sugar-phosphate links to encode genetic information. The oligomer assumes a duplex with extended nucleotide repeats formed out of mostly N-type sugar puckers. With the exception of the 5¢-terminal guanine that assumes thesyn glycosyl conformation, all other bases prefer theantiglycosyl conformation. Base pairs in the duplex exhibit slide () A ˚ ) and intermediate values for X-displacement () A ˚ ), as in ADNA, while their inclination to the helical axis is not prominent. .
