Effect of phosphorothioate chirality on i-motif structure and stability.
Effect of phosphorothioate chirality on i-motif structure and stability.
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DOI：
10.1021/bi035419r
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发表时间：
2004-05
期刊：
影响因子：
2.9
通讯作者：
K. Kanaori;S. Sakamoto;H. Yoshida;P. Guga;W. Stec;K. Tajima;K. Makino
中科院分区：
文献类型：
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作者：
K. Kanaori;S. Sakamoto;H. Yoshida;P. Guga;W. Stec;K. Tajima;K. Makino
P-手性立体定义的硫代磷酸酯基团已被引入到 d(T(PS1)C(PS2)C(PS3)C(PS4)C)（PSn = 硫代磷酸酯基团）的所有四个核苷酸间位置，并且在 PS-d(TC(4)) 的 16 种可能的非对映体中，合成了 10 个立体异构体，以研究 P-手性意义对 i-基序的结构和稳定性的影响结构。圆二色光谱的温度依赖性表明，[all R(p)]-PS-d(TC(4)) i-motif 的熔解温度 (T(m)) 为 31 ℃，与母体低聚物 PO-d(TC(4)) 相同，而 [all S(p)]-PS-d(TC(4)) i-motif 的熔解温度大幅降低了 11 ℃。 S(p) 导致 PS1、PS2 和 PS3 位置处的 T(m) 降低 3-4 摄氏度，PS4 位置处降低 1 摄氏度，显示了 T(m) 抑制的累加特性。 [all R(p)]-PS-、[all S(p)]-PS-和 PO-d(TC(4)) 之间的 NOESY 谱比较表明，全 S(p) 异构体的残基内 H6-H3' 和 H2' '-H4' NOE 交叉峰弱于全 R(p) 异构体和 PO-d(TC(4)) 的 NOE 交叉峰，表明 C3'-endo 构象和糖苷键角。 [所有 S(p)]-PS-d(TC(4)) 形成的 i-基序的结构交替也由 C2/C3/C4 H2'' 和 H4' 质子与 [所有 R(p)]-PS-d(TC(4)) 和 PO-d(TC(4)) 的化学位移差异表明。这些结果表明，硫代磷酸酯键的磷上的S(p)构型改变了窄沟中的糖-硫代磷酸酯构象和分子间相互作用，导致i基序结构不稳定。
The P-chiral stereo-defined phosphorothioate groups have been introduced into all of the four internucleotide positions of d(T(PS1)C(PS2)C(PS3)C(PS4)C) (PSn = phosphorothioate group), and among the 16 possible diastereomers of PS-d(TC(4)), 10 stereomers have been synthesized to investigate the effects of the sense of the P-chirality upon the structure and stability of the i-motif structure. The temperature dependence of circular dichroism spectra showed that the melting temperature (T(m)) of the [all R(p)]-PS-d(TC(4)) i-motifs was 31 degrees C, identical to that of the parent oligomer, PO-d(TC(4)), while that of the [all S(p)]-PS-d(TC(4)) i-motif was largely decreased by 11 degrees C. Single substitution of R(p) with S(p) caused a decrease of T(m) by 3-4 degrees C at positions of PS1, PS2, and PS3 and by 1 degrees C at that of PS4, showing the additive property of the T(m) suppression. The comparison of the NOESY spectra between [all R(p)]-PS-, [all S(p)]-PS-, and PO-d(TC(4)) showed that intraresidual H6-H3' and H2' '-H4' NOE cross-peaks of the all S(p) isomer are weaker than those of the all R(p) isomer and PO-d(TC(4)), indicating the change in the C3'-endo conformation and glycosidic bond angle. The structural alternation for the i-motif formed by [all S(p)]-PS-d(TC(4)) is also suggested by the chemical shift differences of C2/C3/C4 H2''and H4' protons from those of [all R(p)]-PS-d(TC(4)) and PO-d(TC(4)). These results suggest that the S(p) configuration at phosphorus of the phosphorothioate linkage changes the sugar-phosphorothioate conformation and intermolecular interaction in the narrow groove, leading to the destabilization of the i-motif structure.