Solid-state deuterium NMR investigation of internal motion in 2'-deoxythymidine
Solid-state deuterium NMR investigation of internal motion in 2'-deoxythymidine
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2-脱氧胸苷内部运动的固态氘核磁共振研究
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
G. Drobny
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作者：
A. Kintanar;T. Alam;W. Huang;D. C. Schindele;D. Wemmer;G. Drobny
采用/sup 2/H核磁共振波谱法表征了2′-脱氧胸苷在固体状态下的动力学特性。制备了三种不同的特异性氘化核苷，分别在甲基，C6位置和5'-亚甲基上标记。分析了/sup 2/H核磁共振四极回波线形状和自旋晶格（T/ sup 1/）弛豫时间，以确定标记部分的运动机制和速率。只有甲基发生了大幅度的运动，它由围绕C/sub 3/对称轴的3次跳跃组成，相关时间为室温/tau//sub C/约。反应的表观活化能（E/sub a/）为5.9 kJ/mol。数据还表明，整个嘧啶碱经历了一个快速的、小幅度的运动，作者将其建模为在平衡位置附近的一个/±/9/度/振动。在298k时，振动发生在相关时间/tau//sub c/附近。嘧啶基的运动也会影响甲基，但增加的运动只会导致室温甲基跳变相关时间的微小变化，/tau//sub c/约。4.2 ps.振动运动对甲基氘核的自旋-晶格弛豫只有很小的贡献，而且这可能对观察到的异常低的表观活化能没有显著的贡献。5'-亚甲基似乎也经历了与嘧啶碱相似的振动（/±/ 10/度/），但相关时间要长得多，/tau//sub c/约。室温下200ns。从运动模型和实验线的形状，他们能够确定氘核在不同位置的不对称参数（/eta/）和四极耦合常数的静态值。«少
/sup 2/H NMR spectroscopy is used to characterize the dynamics of 2'-deoxythymidine in the solid state. Three different specifically deuteriated nucleosides were prepared, with labels at the methyl group, at the C6 position, and at the 5'-methylene group, respectively. The /sup 2/H NMR quadrupole echo line shapes and spin-lattice (T/sub 1/) relaxation times were analyzed to determine the mechanism and rate of motion of the labeled moieties. Only the methyl group undergoes large-amplitude motion, which consists of 3-fold jumps about the C/sub 3/ symmetry axis with a room-temperature correlation time /tau//sub c/ approx. 3.0 ps. The apparent activation energy (E/sub a/) for this process is 5.9 kJ/mol. The data also indicate that the entire pyrimidine base undergoes a rapid, small-amplitude motion, which the authors have modeled as a /plus minus/9/degrees/ libration about the equilibrium position. At 298 K, the libration occurs with correlation time /tau//sub c/ approx. 1.0 ps. The motion of the pyrimidine base also affects the methyl group, but the added motion causes only a small variation in the room-temperature methyl jump correlation time, /tau//sub c/ approx. 4.2 ps. The librational motion makes only a small contribution to the spin-lattice relaxation of the methyl deuterons, and this likelymore » does not contribute significantly to the unusually low value of the apparent activation energy that is observed. The 5'-methylene group also appears to be undergoing a similar libration (/plus minus/ 10/degrees/) as the pyrimidine base but with a much longer correlation time, /tau//sub c/ approx. 200 ns at room temperature. From the models of motion and the experimental line shapes, they are able to determine the static values of the asymmetry parameter (/eta/) and the quadrupole coupling constant for deuterons at the various sites.« less