Ding D, Grayaznov S M, Lloyd D H, Chandrasekaran S, Yao S, Ratmeyer L, Pan Y, Wilson W D
Department of Chemistry, Georgia State University, Atlanta, 30303, USA.
Nucleic Acids Res. 1996 Jan 15;24(2):354-60. doi: 10.1093/nar/24.2.354.
The solution conformations of the dinucleotide d(TT) and the modified duplex d(CGCGAATTCGCG)2 with N3'--> P5' phosphoramidate internucleoside linkages have been studied using circular dichroism (CD) and NMR spectroscopy. The CD spectra indicate that the duplex conformation is similar to that of isosequential phosphodiester RNA, a A-type helix, and is different from that of DNA, a B-type helix, NMR studies of model dimers d(TpT) and N3'--> P5' phosphoramidate d(TnpT) show that the sugar ring conformation changes from predominantly C2'-endo to C3'-endo when the 3'-phosphoester is replaced by a phosphoramidate group. Two-dimensional NMR (NOESY, DQF-COSY and TOCSY spectra) studies of the duplex provide additional details about the A-type duplex conformation of the oligonucleotide phosphoramidate and confirm that all furanose rings of 3'-aminonucleotides adopt predominantly N-type sugar puckering.
已使用圆二色性（CD）和核磁共振光谱法研究了具有N3'→P5'氨基磷酸酯核苷间连接的二核苷酸d（TT）和修饰双链体d（CGCGAATTCGCG）2的溶液构象。CD光谱表明，该双链体构象与等序列磷酸二酯RNA（A型螺旋）的构象相似，与DNA（B型螺旋）的构象不同。对模型二聚体d（TpT）和N3'→P5'氨基磷酸酯d（TnpT）的核磁共振研究表明，当3'-磷酸酯被氨基磷酸酯基团取代时，糖环构象从主要的C2'-内向型转变为C3'-内向型。对该双链体的二维核磁共振（NOESY、DQF-COSY和TOCSY光谱）研究提供了有关寡核苷酸氨基磷酸酯A型双链体构象的更多细节，并证实3'-氨基核苷酸的所有呋喃糖环主要采用N型糖折叠。
