Ion binding to nucleosides. A 35C1 and 7Li NMR study.
Ion binding to nucleosides. A 35C1 and 7Li NMR study.
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离子与核苷结合。
DOI：
10.1021/ja00441a017
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发表时间：
1976
影响因子：
15
通讯作者：
R. Sharp
中科院分区：
文献类型：
--
作者：
A. C. Plaush;R. Sharp
7 Li和35 C1核磁弛豫时间的大的变化时，观察到核苷，碱基，和核糖添加到氯化锂在DMSO中的解决方案。T1的摩尔缩短对所研究的溶质中特定官能团的存在非常敏感，并且显示出反映了Cl-和Li+与溶质上的特定位点的结合。已研究了与鸟苷、1-甲基鸟苷、肌苷、腺苷、尿苷、<$-胸苷、胞苷、腺嘌呤、胸腺嘧啶、尿嘧啶、胞嘧啶和核糖的结合。已发现三个结合位点：（1）Cl-与鸟苷的（N1-H，C2-NH 2）区域结合较强，与其类似物1-甲基鸟苷和肌苷的相应区域结合较弱;（2）Li+与胞苷和胞嘧啶的N3位点结合，阻碍相邻氨基的旋转;（3）LiCl可能以离子对的形式与所研究的所有核苷的呋喃糖环结合;在离子弛豫数据中没有发现这种结合的证据。尿嘧啶、胸腺嘧啶和腺嘌呤在T1数据中没有显示结合的证据，尽管这些碱基中NH和NH 2基团的质子共振发生了化学位移。在所有其他情况下，质子化学位移一般证实从弛豫数据得出的推论。已推导出等锂常数、弛豫速率和总浓度之间的关系，并用于估计核糖位点中7 Li的缔合常数和弛豫速率。大量实验证据表明，二价金属离子与核苷、核苷酸和核酸结合（Izatt等人2a和Phillips 21”对该主题进行了综述）。许多金属离子与核苷酸和核酸的磷酸酯的结合已经通过3 IP NMR、电位测定法、IR和拉曼光谱法被广泛地证实。核磁共振（和15 N）和电位测量也表明，某些二价金属（如Cu ~（2+）3）结合到嘌呤和嘧啶碱基的特定位点上。顺磁性离子对结合位点附近质子的共振产生特别显著的影响。这些共振通过空间偶极耦合选择性地加宽或移动。3· 4反磁性离子通常产生小得多的NMR效应，除了直接参与离子配位的NH和OH基团。由于与溶剂质子的快速交换，这些基团中的质子在水溶液的NMR光谱中不可见，但可以在没有可交换质子的溶剂（如DMSO）中观察到。
Large variations in 7Li and 35C1 nuclear magnetic relaxation times are observed when nucleosides, bases, and ribose are added to LiCl solutions in DMSO. The molar shortening of T\is very sensitive to the presence of specific functional groups in the solutes studied and is shown to reflect binding by Cl” and Li+ to specific sites on the solutes. Binding to guanosine, 1-methylguanosine, inosine, adenosine, uridine,¿-thymidine, cytidine, adenine, thymine, uracil, cytosine, and ribose has been studied. Three binding sites have been found:(1) Cl-binds strongly to the (Nj-H, C2-NH2) region of guanosine, and more weakly to thecorresponding regions of its analogues, 1-methylguanosine and inosine;(2) Li+ binds to the N3 site of cytidine and cytosine hindering rotation of the adjacent amino group;(3) LiCl binds, probably as an ion pair, to the furanose ringof all ribosides studied;¿-thymidine shows no evidence of this binding inthe ion relaxation data. Uracil, thymine, and adenine show no evidence of bindingin the T\data although proton resonances of NH and NH2 groups in thesebases are chemically shifted. In all other cases proton chemical shifts generally confirm inferences drawn from relaxation data. Relations between the equi-librium constants, relaxation rates, and total concentrations have been derived and used to estimate the association constant and relaxation rate for 7Li in the ribose site.A substantial body of experimental evidence has shown that divalent metal ions bind to nucleosides, nucleotides, and nucleic acids (this subject has been reviewed by Izatt et al. 2a and Phillips21”). Thebinding of many metal ions to phosphate esters of nucleotides and nucleic acids has been extensively documented by 3IP NMR, potentiometry, and IR and Raman spectroscopy. NMR (and 15N) and potentiometric mea-surements have also shown that certain divalent metals (eg, Cu2+ 3) bind to specific sites on purine and pyrimidine bases. Paramagnetic ions produce particularly striking effects on resonances of protons near the binding site. These resonances are selectively broadened or shifted by through-space dipolar couplings. 3· 4 Diamagnetic ions generally produce much smaller NMR effects exceptat NH and OH groups that are directly involved in coordination to the ions. Protons in these groups are not visible in NMR spectra of aqueous solutions due to rapid exchange with the solvent protons but can be observed in solvents that have no exchangeable protons, such as DMSO.