Field dependence of chemically induced dynamic nuclear polarization (CIDNP) in the photoreaction of N-acetyl histidine with 2,2′-dipyridyl in aqueous solution
Field dependence of chemically induced dynamic nuclear polarization (CIDNP) in the photoreaction of N-acetyl histidine with 2,2′-dipyridyl in aqueous solution
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DOI：
10.1021/jp004582i
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发表时间：
2001-07-05
影响因子：
2.9
通讯作者：
Vieth, HM
中科院分区：
文献类型：
--
作者：
Grosse, S;Yurkovskaya, AV;Vieth, HM
化学诱导的动态核极化（CIDNP）的氨基酸染料（组氨酸联吡啶）光反应系统的影响进行了测量，在0和7 T之间的范围内使用一种新型的机械场循环单元与快速数字定位的高分辨率NMR探头在空间变化的磁场。H-1 CIDNP效应在β-位的CH 2质子和咪唑环上的两个质子（H-2和H-4）中观察到。对于在β-位置的质子，观察到多重态效应，其具有随磁场变化的偏振模式。通过对自旋章动的分析，确定了核能级间的非玻耳兹曼布居差。在低于20 mT的“零场字符”的多重态效应占主导地位的对称自旋波函数的优先填充状态。同样地，对于两个组氨酸环质子，发现具有发射/吸收多重峰图案的强极化。在20和300 mT之间，在20 mT以下变为零场特征。叠加的是两个质子的发射性CIDNP（净效应）。在0.1 T以上，环质子净效应变为吸收性的，并且在7 T左右极化呈现其最大值。在高场近似下对场依赖性的数值模拟与在0.1 ~ 7 T的场范围内获得的实验数据非常一致。分析了不同动力学过程对CIDNP形成的影响及其场依赖性。讨论了CIDNP在蛋白质结构和折叠过程研究中磁场强度的优化。
Chemically induced dynamic nuclear polarization (CIDNP) effects for the amino acid-dye (histidine-dipyridyl) photoreaction system are measured in the range between 0 and 7 T using a novel mechanical field cycling unit with fast digital positioning of a high-resolution NMR probe in a spatially varying magnetic field. H-1 CIDNP effects are observed for the CH2 protons in beta -position and for two protons (H-2 and H-4) at the imidazole ring. For the protons in beta -position a multiplet effect is observed having a polarization pattern that changes with the magnetic field. By analysis of the spin nutation, the non-Boltzmann population differences among the nuclear levels are determined. At a field below 20 mT "zero-field character" of the multiplet effect prevails corresponding to preferentially populated states with Symmetric spin wave functions. Likewise, for the two histidine ring-protons strong polarization with an emission/absorption multiplet pattern is found. between 20 and 300 mT changing below 20 mT to zero-field character. Superimposed is emissive CIDNP (net effect) for both protons. Above 0.1 T, the ring proton net effect turns absorptive and around 7 T the polarization exhibits its maximum. Numerical simulations of the field dependence in high field approximation are in very good agreement with the experimental data obtained at fields ranging from 0.1 to 7 T. The influence of different dynamic processes on the CIDNP formation and its field dependence is analyzed. Optimization of the magnetic field strength for CIDNP application in studies of protein structure and folding process is discussed.