Lee M, Coulter D M, Pon R T, Krowicki K, Lown J W
Department of Chemistry, University of Alberta, Edmonton, Canada.
J Biomol Struct Dyn. 1988 Apr;5(5):1059-87. doi: 10.1080/07391102.1988.10506449.
The non-exchangeable and imino proton NMR resonances of the non self-complementary decadeoxyribonucleotide d-[(GATCCGTATG).(GATACGGATC)] as well as those of the 1:1 complex of the monocatonic bis-imidazole lexitropsin 1 to this sequence have been assigned by using a combination of NOE difference, COSY and NOESY techniques. Confirmation of complete annealing of the two non self-complementary decamer strands to give the duplex decadeoxyribonucleotide is obtained by the detection of ten imino protons. It is established that the sugar-base orientations of all the bases in the duplex decamer are anti. From NOE studies, it is concluded that the duplex oligomer is right-handed and adopts a conformation in solution that belongs to the B family. A population analysis reveals that the sugar moieties exist predominantly in the S-form (2'-endo-3'-exo). Addition of 1 to the DNA solution leads to doubling of the resonances for CH6(4,5), GH8(6), TH6(7) and T-CH3(7). The base, anomeric H1' and imino proton signals for the base sequence 5'-CCGT undergo the most marked drug-induced chemical shift changes. These results provide evidence that the lexitropsin is bound to the sequence 5'-CCGT in the minor groove of the DNA. NOE measurements between the amide protons (NH1 and NH4) and the imino proton (IV and V) signals confirmed the location and orientation of 1 in the 1:1 complex, with the imino terminus oriented to C(4). The specific binding of 1 to the sequence 5'-CCGT-3' deduced in this study is in agreement with the footprinting data obtained using the Hind III/Nci fragment from pBR322 DNA [Kissinger et al. 1987 (13)]. Intramolecular NOEs observed between H4 and H9 of the lexitropsin suggest that the molecule is not planar, but subjected to propeller twisting, in both the free and bound forms. Furthermore, NOE measurements permit assignment of the DNA duplex in the 1:1 complex to the B-form, which is similar to that of the free DNA. The [(T7A8T9).(A12T13A14)] segment of the DNA shows better stacking, by propeller twisting, compared to the rest of the molecule in the free as well as the complex forms. The intermolecular rate of exchange of 1 between the equivalent 5'-CCGT sites, at a concentration of 12 mM, is estimated to be approximately 88s-1 at 308 degrees K with delta G not equal to of 63 +/- 5 KJ mol-1.
通过结合使用核Overhauser效应（NOE）差异、同核自旋-自旋偶合相关谱（COSY）和核Overhauser效应相关谱（NOESY）技术，已对非自互补的十聚脱氧核糖核苷酸d-[(GATCCGTATG).(GATACGGATC)]以及单阳离子双咪唑型勒克西特罗辛1与该序列的1:1复合物的不可交换质子和亚氨基质子的核磁共振（NMR）共振峰进行了归属。通过检测到十个亚氨基质子，证实了两条非自互补的十聚体链完全退火形成双链十聚脱氧核糖核苷酸。已确定双链十聚体中所有碱基的糖-碱基取向均为反式。从NOE研究得出，双链寡聚物是右手螺旋的，并且在溶液中采用属于B家族的构象。群体分析表明，糖部分主要以S型（2'-内型-3'-外型）存在。向DNA溶液中加入1会导致CH6(4,5)、GH8(6)、TH6(7)和T-CH3(7)的共振峰翻倍。对于碱基序列5'-CCGT，碱基、异头H1'和亚氨基质子信号发生了最显著的药物诱导化学位移变化。这些结果提供了证据，表明勒克西特罗辛与DNA小沟中的序列5'-CCGT结合。酰胺质子（NH1和NH4）与亚氨基质子（IV和V）信号之间的NOE测量证实了1在1:1复合物中的位置和取向，亚氨基末端朝向C(4)。本研究中推断的1与序列5'-CCGT-3'的特异性结合与使用来自pBR322 DNA的Hind III/Nci片段获得的足迹数据一致[基辛格等人，1987年（13）]。在勒克西特罗辛的H4和H9之间观察到的分子内NOE表明，该分子在游离和结合形式下都不是平面的，而是存在螺旋扭曲。此外，NOE测量允许将1:1复合物中的DNA双链体归为B型，这与游离DNA的B型相似。与游离形式以及复合物形式的分子其余部分相比，DNA的[(T7A8T9).(A12T13A14)]片段通过螺旋扭曲表现出更好的堆积。在308 K、浓度为12 mM时，1在等效的5'-CCGT位点之间的分子间交换速率估计约为88 s-1，自由能变化量ΔG不等于63±5 kJ mol-1。
