International Tomography Center, Institutskaya 3a, 630090 Novosibirsk, Russia.
Phys Chem Chem Phys. 2011 Apr 14;13(14):6619-27. doi: 10.1039/c0cp02449j. Epub 2011 Mar 7.
Chemically Induced Dynamic Nuclear Polarization (CIDNP) of the diamagnetic products of radical reactions is exploited for the purpose of determination of the hyperfine coupling constants (HFCCs) of the radical intermediates. A simple proportionality relation between geminate CIDNP of a nucleus and its HFCC at the radical stage is established. The applicability range of this relation is determined: the relation is fulfilled in the case of a large difference in g-factor between the radicals involved and for the situation where the number of magnetic nuclei in the system is sufficiently large. The validity of the relation was confirmed by CIDNP experiments on radical pairs with precisely known HFCCs. Using the proportionality relation we were able to measure the HFCCs in various short-lived radicals of the amino acids histidine and tryptophan and of the S-N-centered cyclic radical of methionine derived from the methionine-glycine dipeptide in aqueous solution.
利用自由基反应的抗磁性产物的化学动态核极化（CIDNP），可以确定自由基中间体的超精细耦合常数（HFCC）。建立了核的成对 CIDNP 与其在自由基阶段的 HFCC 之间的简单比例关系。确定了该关系的适用范围：在涉及的自由基的 g 因子差异较大的情况下，以及在系统中的磁核数量足够大的情况下，该关系成立。通过对具有精确已知 HFCC 的自由基对的 CIDNP 实验，验证了该关系的有效性。利用比例关系，我们能够测量水溶液中来自蛋氨酸-甘氨酸二肽的甲硫氨酸的 S-N 中心环状自由基以及组氨酸和色氨酸的各种短寿命自由基中的 HFCC。
