Sezer Deniz, Gafurov Marat, Prandolini M J, Denysenkov Vasyl P, Prisner Thomas F
Institut für Physikalische und Theoretische Chemie, J. W. Goethe-Universität, 60438 Frankfurt am Main, Germany.
Phys Chem Chem Phys. 2009 Aug 21;11(31):6638-53. doi: 10.1039/b906719c. Epub 2009 Jul 6.
The interaction between nuclear and electronic spins is of interest for structural characterization of biomolecules and biomedical imaging based on nuclear magnetic resonance. The polarization of the nuclear spins can be increased significantly if the electron spin polarization is kept out of equilibrium. We employ semiclassical relaxation theory to analyze the electronic polarization of the two-spin system characteristic of nitroxide radicals. Atomistic molecular dynamics simulations of the nitroxide TEMPOL in water are performed to account for the effects of tumbling and spin-rotation coupling on the spin-spin and spin-lattice relaxation times. Concentration effects on the electron saturation are introduced by allowing for Heisenberg spin exchange between two nitroxides. Polarization enhancement profiles, calculated from the computed saturation, are directly compared with liquid-state dynamic nuclear polarization experiments conducted at 260 GHz/400 MHz. The contribution of the separate hyperfine lines to the saturation can be easily disentangled using the developed formalism.
核自旋与电子自旋之间的相互作用对于基于核磁共振的生物分子结构表征和生物医学成像具有重要意义。如果电子自旋极化保持非平衡状态，核自旋的极化可以显著增加。我们采用半经典弛豫理论来分析氮氧化物自由基特征的双自旋系统的电子极化。进行了水中氮氧化物TEMPOL的原子分子动力学模拟，以考虑翻滚和自旋-旋转耦合对自旋-自旋和自旋-晶格弛豫时间的影响。通过考虑两个氮氧化物之间的海森堡自旋交换，引入了浓度对电子饱和的影响。从计算得到的饱和度计算出的极化增强曲线，直接与在260 GHz/400 MHz下进行的液态动态核极化实验进行比较。使用所开发的形式主义，可以很容易地解开单独超精细线对饱和度的贡献。
