Preprints
https://doi.org/10.5194/mr-2022-23
https://doi.org/10.5194/mr-2022-23
 
14 Dec 2022
14 Dec 2022
Status: a revised version of this preprint was accepted for the journal MR and is expected to appear here in due course.

Paramagnetic relaxivity of delocalized long-lived states of protons in chains of CH2 groups

Aiky Razanahoera, Anna Sonnefeld, Geoffrey Bodenhausen, and Kirill Sheberstov Aiky Razanahoera et al.
  • Department of chemistry, École Normale Supérieure, PSL University, 75005 Paris, France

Abstract. Long-lived states (LLS) have lifetimes TLLS that can be much longer than longitudinal relaxation times T1. In molecules containing several geminal pairs of protons in neighbouring CH2 groups, it has been shown that delocalized long-lived states can be excited by converting magnetization into imbalances between the populations of singlet and triplet states of each pair. Since the yield of conversion of observable magnetization into LLS and back are on the order of 10 % or less if one uses spin-locked induced crossing (SLIC), it would be desirable to boost the sensitivity by dissolution dynamic nuclear polarization (d-DNP). To enhance the magnetization of nuclear spins by d-DNP, the analytes must be mixed with radicals such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL) prior to freezing at low temperatures in the vicinity of 1 K. After dissolution, these radicals lead to an undesirable paramagnetic relaxation enhancement (PRE) which shortens not only the longitudinal relaxation times T1 but also the lifetimes TLLS of long-lived states. It is confirmed in this work that PRE by TEMPOL is less deleterious for LLS than for longitudinal magnetization for four different molecules: 2,2-dimethyl-2-silapentane-5-sulfonate (DSS), homotaurine, taurine, and acetylcholine. The relaxivities (i.e., the slopes of relaxation rates as a function of the radical concentration) of LLS rLLS are 3 to 5 times smaller than the relaxivities of longitudinal magnetization r1. Partial delocalization of the LLS across neighbouring CH2 groups may decrease this advantage, but in practice, this effect was observed to be minor when comparing taurine containing two CH2 groups and homotaurine with three CH2 groups. Regardless of whether the LLS are delocalized or not, it is shown that PRE should not be a major problem for experiments combining d DNP and LLS, provided the concentration of paramagnetic species after dissolution does not exceed 1 mM, a condition that is readily fulfilled in typical d-DNP experiments. In bullet d-DNP experiments, however, it may be necessary to reduce TEMPOL by adding ascorbate or using lower concentrations of TEMPOL.

Aiky Razanahoera et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on mr-2022-23', Malcolm Levitt, 24 Dec 2022
  • RC2: 'Comment on mr-2022-23', Alexej Jerschow, 24 Dec 2022
  • RC3: 'Comment on mr-2022-23', Anonymous Referee #3, 04 Jan 2023
  • AC1: 'Comment on mr-2022-23', Kirill Sheberstov, 18 Jan 2023
  • EC1: 'Comment on mr-2022-23', Gottfried Otting, 19 Jan 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on mr-2022-23', Malcolm Levitt, 24 Dec 2022
  • RC2: 'Comment on mr-2022-23', Alexej Jerschow, 24 Dec 2022
  • RC3: 'Comment on mr-2022-23', Anonymous Referee #3, 04 Jan 2023
  • AC1: 'Comment on mr-2022-23', Kirill Sheberstov, 18 Jan 2023
  • EC1: 'Comment on mr-2022-23', Gottfried Otting, 19 Jan 2023

Aiky Razanahoera et al.

Data sets

Paramagnetic relaxivity of delocalized long-lived states of protons in chains of CH2 groups Razanahoera Aiky; Sonnefeld Anna; Bodenhausen Geoffrey; Sheberstov Kirill https://doi.org/10.5281/zenodo.7432635

Aiky Razanahoera et al.

Viewed

Total article views: 342 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
264 61 17 342 7 4
  • HTML: 264
  • PDF: 61
  • XML: 17
  • Total: 342
  • BibTeX: 7
  • EndNote: 4
Views and downloads (calculated since 14 Dec 2022)
Cumulative views and downloads (calculated since 14 Dec 2022)

Viewed (geographical distribution)

Total article views: 326 (including HTML, PDF, and XML) Thereof 326 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 28 Jan 2023
Download
Short summary
In this work, we study the relaxivity of long-lived states (LLS) excited across two to three CH2 groups in 4 different compounds and find that commonly used polarising agent in dissolution-dynamic nuclear polarization (d-DNP) does not enhance relation significantly. This result is important for future implementation of d-DNP hyperpolarization of LLS.