Okuno Yusuke, Cavagnero Silvia
Department of Chemistry, University of Wisconsin - Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
J Phys Chem B. 2016 Feb 4;120(4):715-23. doi: 10.1021/acs.jpcb.5b12339. Epub 2016 Jan 22.
Photochemically induced dynamic nuclear polarization (photo-CIDNP) is a powerful approach for sensitivity enhancement in NMR spectroscopy. In liquids, intermolecular photo-CIDNP depends on the transient bimolecular reaction between photoexcited dye and sample of interest. Hence the extent of polarization is sample-concentration dependent. This study introduces fluorescein (FL) as a photo-CIDNP dye whose performance is exquisitely tailored to data collection at extremely low sample concentrations. The photo-CIDNP resonance intensities of tryptophan in the presence of either FL or FMN (i.e., the routinely employed flavin mononucleotide photosensitizer) in the liquid state show that FL yields superior sensitivity and enables rapid data collection down to an unprecedented 1 μM concentration. This result was achieved on a conventional spectrometer operating at 14.1 T and equipped with a room-temperature probe (i.e., noncryogenic). Kinetic simulations show that the excellent behavior of FL arises from its long excited-state triplet lifetime and superior photostability relative to conventional photo-CIDNP sensitizers.
光化学诱导动态核极化（光化学诱导动态核极化，photo-CIDNP）是核磁共振光谱中提高灵敏度的一种强大方法。在液体中，分子间光化学诱导动态核极化取决于光激发染料与感兴趣样品之间的瞬态双分子反应。因此，极化程度取决于样品浓度。本研究引入了荧光素（FL）作为一种光化学诱导动态核极化染料，其性能经过精心调整，适用于极低样品浓度下的数据采集。在液态下，色氨酸在存在FL或FMN（即常规使用的黄素单核苷酸光敏剂）的情况下的光化学诱导动态核极化共振强度表明，FL具有更高的灵敏度，能够以前所未有的1 μM浓度进行快速数据采集。这一结果是在一台运行于14.1 T且配备室温探头（即非低温探头）的传统光谱仪上实现的。动力学模拟表明，FL的优异性能源于其较长的激发态三重态寿命以及相对于传统光化学诱导动态核极化敏化剂而言更好的光稳定性。
