Service de Physique de l'Etat Condensé

Boosting the signal of nuclear magnetic resonance spectroscopy by orders of magnitude using dissolution-DNP: observations, biological applications and future prospects
  - ENS - Département de chimie, PSL University, Sorbonne Université, CNRS, Paris, France
Mercredi 03/04/2019, 11h15-12h15
SPEC Salle Itzykson, Bât.774, Orme des Merisiers

Dynamic nuclear polarization (DNP) has been known for several decades as a particularly powerful and versatile way to enhance nuclear spin polarization, therefore sensitivity. Thus, at low temperatures, the microwave irradiation of the electron spin transition of paramagnetic impurities present in a sample of nuclear spins allows one to transfer the extremely high electron spin polarization to the nuclear spins to which they are coupled (see [1,2] for early reviews). DNP has regained interest in the early 2000s with the invention of the coupling of DNP to the dissolution of the polarized substrate into a solution at room temperature, thereby allowing fantastic sensitivity enhancements of several orders of magnitude (~104).[3] and paving the way to a wide range of applications. In this presentation, I will discuss selective illustrations of the applications and problems encountered in our lab in the past few years, and situated at both ends of the D-DNP process. On the one hand, we observed characteristic MASER oscillations from a sample of (frozen) water. At the same time, the free induction signal was found to persist for several tens of seconds, even in the absence of microwave irradiation. The interpretation of these experiments in terms of the Bloch-Maxwell- Provotorov equations, [4,5] though qualitative, nevertheless provides physical insight into our observations. On the other hand, DDNP has been used for the study of enzyme kinetics in solution on short time scales, with a time resolution lower than the second. Examples from the pentose phosphate pathway, one of the critical metabolic pathways in the cell, will be shown. The interesting case of the spontaneous rearrangement and hydrolysis of 6-phosphogluconolactone, “side-reactions” occurring in the PPP, will be discussed.[5]
References
[1] A. Abragam, M. Goldman, Rep. Prog. Phys., 41, 395, 1978
[2] V. A. Atsarkin, M. I. Rodak, Usp. Fiz. Nauk 107, 3-27, 1972
[3] J.H. Ardenkjær-Larsen, B. Fridlund, A. Gram, G. Hansson, L. Hansson, M.H. Lerche, R. Servin,
M. Thaning, K. Golman, 100, 10158-10163, 2003
[4] P. Bösiger, E. Brun, D. Meier, Phys. Rev. A, 18, 671-684, 1978
[5] E. Weber et al., in preparation
[6] A. Sadet, E. M.M. Weber, A. Jhajharia, D. Kurzbach, G. Bodenhausen, E. Miclet, D. Abergel,
Chem. Eur.J. 24, 5456-5461, 2018
Acknowledgements
This work was supported by the French ANR (project ENZYPOL), the European Research Council
(contract“Dilute Para-Water”). We thank Bruker BioSpin

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