Kaucher Mark S, Lam Yui-Fai, Pieraccini Silvia, Gottarelli Giovanni, Davis Jeffery T
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.
Chemistry. 2004 Dec 17;11(1):164-73. doi: 10.1002/chem.200400782.
This paper presents results from a series of pulsed field gradient (PFG) NMR studies on lipophilic guanosine nucleosides that undergo cation-templated assembly in organic solvents. The use of PFG-NMR to measure diffusion coefficients for the different aggregates allowed us to observe the influences of cation, solvent and anion on the self-assembly process. Three case studies are presented. In the first study, diffusion NMR confirmed formation of a hexadecameric G-quadruplex G 14 K(+)4 pic(-) in CD(3)CN. Furthermore, hexadecamer formation from 5'-TBDMS-2',3'-isopropylidene G 1 and K(+) picrate was shown to be a cooperative process in CD(3)CN. In the second study, diffusion NMR studies on 5'-(3,5-bis(methoxy)benzoyl)-2',3'-isopropylidene G 4 showed that hierarchical self-association of G(8)-octamers is controlled by the K(+) cation. Evidence for formation of both discrete G(8)-octamers and G(16)-hexadecamers in CD(2)Cl(2) was obtained. The position of this octamer-hexadecamer equilibrium was shown to depend on the K(+) concentration. In the third case, diffusion NMR was used to determine the size of a guanosine self-assembly where NMR signal integration was ambiguous. Thus, both diffusion NMR and ESI-MS show that 5'-O-acetyl-2',3'-O-isopropylidene G 7 and Na(+) picrate form a doubly charged octamer G 72 Na(+)2 pic(-) 9 in CD(2)Cl(2). The anion's role in stabilizing this particular complex is discussed. In all three cases the information gained from the diffusion NMR technique enabled us to better understand the self-assembly processes, especially regarding the roles of cation, anion and solvent.
本文展示了一系列关于亲脂性鸟苷核苷的脉冲场梯度（PFG）核磁共振研究结果，这些核苷在有机溶剂中发生阳离子模板组装。使用PFG-NMR测量不同聚集体的扩散系数，使我们能够观察阳离子、溶剂和阴离子对自组装过程的影响。文中给出了三个案例研究。在第一个研究中，扩散核磁共振证实了在CD(3)CN中形成了十六聚体G-四链体G 14 K(+)4 pic(-)。此外，在CD(3)CN中，由5'-叔丁基二甲基硅烷基-2',3'-异亚丙基G 1和苦味酸钾形成十六聚体是一个协同过程。在第二个研究中，对5'-(3,5-双(甲氧基)苯甲酰基)-2',3'-异亚丙基G 4的扩散核磁共振研究表明，G(8)-八聚体的分级自缔合受K(+)阳离子控制。在CD(2)Cl(2)中获得了离散的G(8)-八聚体和G(16)-十六聚体形成的证据。结果表明，这种八聚体-十六聚体平衡的位置取决于K(+)浓度。在第三个案例中，当核磁共振信号积分不明确时，使用扩散核磁共振来确定鸟苷自组装体的大小。因此，扩散核磁共振和电喷雾电离质谱（ESI-MS）均表明，5'-O-乙酰基-2',3'-O-异亚丙基G 7和苦味酸钠在CD(2)Cl(2)中形成了双电荷八聚体G 72 Na(+)2 pic(-) 9。文中讨论了阴离子在稳定这种特定复合物中的作用。在所有这三个案例中，从扩散核磁共振技术获得的信息使我们能够更好地理解自组装过程，特别是关于阳离子、阴离子和溶剂的作用。
