Department of Physics, University of Pavia , 27100 Pavia, Italy.
NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University , Padualaan 8, 3584 CH Utrecht, The Netherlands.
J Phys Chem B. 2018 Feb 15;122(6):1836-1845. doi: 10.1021/acs.jpcb.7b11950. Epub 2018 Feb 1.
H and C dynamic nuclear polarizations have been studied in C-enriched β-cyclodextrins doped with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl free radical. H and C polarizations raised above 7.5 and 7%, respectively, and for both nuclear species, the transfer of polarization from the electron spins appears to be consistent with a thermal mixing scenario for a concentration of 9 C nuclei per molecule. When the concentration is increased to 21 C nuclei per molecule, a decrease in the spin-lattice relaxation and polarization buildup rates is observed. This reduction is associated with the bottleneck effect induced by the decrease in the number of electron spins per nucleus when both the nuclear spin-lattice relaxation and the polarization occur through the electron non-Zeeman reservoir. C nuclear spin-lattice relaxation has been studied in the 1.8-340 K range, and the effects of internal molecular motions and of the free radicals on the relaxation are discussed. C hyperpolarization performances and room-temperature spin-lattice relaxation times show that these are promising materials for future biomedical applications.
研究了富 C 的 β-环糊精中掺杂（2,2,6,6-四甲基哌啶-1-基）氧自由基的 H 和 C 动态核极化。H 和 C 的极化分别提高到 7.5%和 7%以上，对于两种核，从电子自旋转移的极化似乎与分子中每个核 9 个 C 核的热混合情况一致。当浓度增加到每个分子 21 个 C 核时，观察到自旋晶格弛豫和极化建立速率下降。这种减少与当核自旋晶格弛豫和极化都通过电子非塞曼储层发生时，每个核的电子自旋数减少引起的瓶颈效应有关。研究了 1.8-340 K 范围内的 C 核自旋晶格弛豫，讨论了内部分子运动和自由基对弛豫的影响。C 超极化性能和室温自旋晶格弛豫时间表明，这些是未来生物医学应用的有前途的材料。
