四链DNA(loopG4)螺旋结构的计算机模拟

HELIX STRUCTURE OF FOUR-STRANDED loopG4: COMPUTER SIMULATIONS

对包含连续鸟嘌呤的寡核苷酸所形成两种反平行四链ＤＮＡ（统称ｌｏｏｐＧ４）的螺旋体部分进行了计算机模拟，给出了各种结构参数，发现ｌｏｏｐＧ４中的磷酸基团呈疏密相间的分布，导致与其抗衡的Ｋ＋亦呈疏密相间的分布。与先前做的平行四链ＤＮＡ相比较，平行Ｇ４的构象能最低，二沟Ｇ４和三沟Ｇ４次之。ｌｏｏｐＧ４中Ｇ四聚体的两种不同堆积方式以背对背的堆积能为低，为实验结果提供了理论支持。还探讨了能量优化过程中Ｇ４－ＤＮＡ的构象变化趋势。

Computer simulations of helix structures of four-stranded loopG4 formed by oligonucleotide containing runs of consecutive guanine bases were performed. Conformational parameters, analysis of energy components and the location of K+ ions were presented. The order of energy is: parallel G4<2grooveG4<3grooveG4. In loopG4 the quartet-stacking energy of back to back is lower than that of face to face. The trend of conformation change during energy minimization was explored. It suggests that different metal ions or different ionic strength may lead to different conformations of G4-DNA.