title: Fluorescein: A Photo-CIDNP Sensitizer Enabling Hypersensitive NMR Data Collection in Liquids at Low Micromolar Concentration.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Wisconsin - Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Okuno
authors.affiliation: Department of Chemistry, University of Wisconsin - Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
authors.forename: Silvia
authors.initials: S
authors.lastname: Cavagnero
mesh_terms: D019793:Fluorescein / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*
chemical_list: D019793:Fluorescein