TY - JOUR

T1 - Molecular features toward high photo-CIDNP hyperpolariztion explored through the oxidocyclization of tryptophan

AU - Torres, Felix

AU - Sobol, Alexander

AU - Greenwald, Jason

AU - Renn, Alois

AU - Morozova, Olga

AU - Yurkovskaya, Alexandra

AU - Riek, Roland

N1 - Funding Information: We would like to thank Daniel Zindel for the synthesis of the 3a-hydroxypyrroloindole diastereoisomer. Y. A. and O. M. acknowledge support by Russian Foundation for Basic Research (projects 20-03-00234 and 19-29-10028). Publisher Copyright: © the Owner Societies 2021. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/3/21

Y1 - 2021/3/21

N2 - Photo-chemically induced dynamic nuclear polarization (photo-CIDNP) is a promising solution to the inherent lack of sensitivity in NMR spectroscopy. It is particularly interesting in biological systems since it operates in water, at room temperature, and it can be repeated if the bleaching of the system can be controlled. However, the photo-CIDNP signal enhancement is well below those of other hyperpolarization techniques. While DNP, PHIP, and SABRE reach polarization enhancements of 103to 104-fold, photo-CIDNP enhancement is typically only one order of magnitude for1H and two orders of magnitude for13C in the amino-acids tryptophan and tyrosine. Here we report on a photo-oxidation product of tryptophan that is strongly photo-CIDNP active under continuous wave light irradiation. In conjunction with the dye Atto Thio 12, a1H signal enhancement of 120-fold was observed on a 600 MHz spectrometer, while at 200 MHz the enhancement was 380-fold. These enhancements in signal to noise correspond to a reduction in measurement time of 14 400-fold and 144 400-fold, respectively. The enhancement for13C is estimated to be over 1200-fold at 600 MHz which corresponds to an impressive measurement time reduction of 1 440 000-fold. This photo-CIDNP active oxidation product of tryptophan has been identified to be 3α-hydroxypyrroloindole. The reasons for its improved signal enhancement compared to tryptophan have been further investigated.

AB - Photo-chemically induced dynamic nuclear polarization (photo-CIDNP) is a promising solution to the inherent lack of sensitivity in NMR spectroscopy. It is particularly interesting in biological systems since it operates in water, at room temperature, and it can be repeated if the bleaching of the system can be controlled. However, the photo-CIDNP signal enhancement is well below those of other hyperpolarization techniques. While DNP, PHIP, and SABRE reach polarization enhancements of 103to 104-fold, photo-CIDNP enhancement is typically only one order of magnitude for1H and two orders of magnitude for13C in the amino-acids tryptophan and tyrosine. Here we report on a photo-oxidation product of tryptophan that is strongly photo-CIDNP active under continuous wave light irradiation. In conjunction with the dye Atto Thio 12, a1H signal enhancement of 120-fold was observed on a 600 MHz spectrometer, while at 200 MHz the enhancement was 380-fold. These enhancements in signal to noise correspond to a reduction in measurement time of 14 400-fold and 144 400-fold, respectively. The enhancement for13C is estimated to be over 1200-fold at 600 MHz which corresponds to an impressive measurement time reduction of 1 440 000-fold. This photo-CIDNP active oxidation product of tryptophan has been identified to be 3α-hydroxypyrroloindole. The reasons for its improved signal enhancement compared to tryptophan have been further investigated.

UR - http://www.scopus.com/inward/record.url?scp=85103349249&partnerID=8YFLogxK

U2 - 10.1039/d0cp06068b

DO - 10.1039/d0cp06068b

M3 - Article

C2 - 33710192

AN - SCOPUS:85103349249

VL - 23

SP - 6641

EP - 6650

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 11

ER -