Direct hyperpolarization of 15N2 singlet states in terminal diazirines enables long lived hyperpolarization and sensitive proton detection - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2018

Direct hyperpolarization of 15N2 singlet states in terminal diazirines enables long lived hyperpolarization and sensitive proton detection

Guannan Zhang
  • Fonction : Auteur
Johannes Collel
  • Fonction : Auteur
Warren Warren
  • Fonction : Auteur
Thomas Theis
  • Fonction : Auteur

Résumé

If selected, I agree to present my work during an oral communication: Yes Abstract: For applications of hyperpolarized compounds, it is attractive to have slow relaxation to allow for complex experimental procedures and to probe slow processes. Particularly slow relaxation can be found in singlet states on pairs of heteronuclei such as 13 C 2 or 15 N 2 [1,2]. A special opportunity presents itself in direct hyperpolarization of heteronuclear singlet states using SABRE (Signal Amplification By Reversible Exchange): Singlet order can be transferred directly from parahydrogen to targeted heteronuclear spin pairs. For example, 15 N 2 in diazirines, one of the smallest 3 membered heterocycles, supports SABRE induced singlet order with decay time constants of above 20 minutes. [1] A remaining challenge in these experiments is that direct detection of 15 N signals is significantly less sensitive than detection on 1 H. Addressing this problem we designed terminal diazirines (R-CH 15 N 2 , see figure, part A) and show that hyperpolarization transfer from 15 N to 1 H enables sensitive detection of relaxation protected states on the more sensitive 1 H channel. Importantly and counter intuition, the close proximity of the proton to the 15 N 2 pair does not significantly reduce the singlet relaxation decay constant T S. Typically, when a proton is brought close to a spin pair, T S becomes significantly shorter because the dipolar coupling induces fast relaxation. This is not the case in a terminal diazirine because of the high symmetry: The dipolar interaction of the protons with each individual 15 N spin is identical. Therefore, the singlet state commutes with the dipolar Hamiltonian and remains protected from this, otherwise detrimental, relaxation channel. We observe singlet decay time constants T S of up to 17.5 min in terminal diazirines (This is a surprisingly small reduction from 20 min T S in non-terminal diazirines). The T S measurements and results from hyperpolarization transfer are illustrated in parts B and C of the Figure. First, it is possible to selectively hyperpolarize either magnetization or singlet order and measure their lifetimes (T 1 and T S) independently. (Polarization levels of ~2% are typical) Next, hyperpolarization transfer efficiencies of up to 70% were observed on 1 H. In conclusion, we have combined long-lived hyperpolarization induced by SABRE on 15 N spin pairs with sensitive detection on 1 H promising hyperpolarized experiments that exceed current approaches in signal lifetimes and sensitivity. Importantly, the employed terminal diazirines can replace methyl groups in biomolecules without significantly altering steric burden and therefore represent a highly promising molecular tag for hyperpolarized experiments. References: 1 Theis, T. et al. Direct and cost-efficient hyperpolarization of long-lived nuclear spin states on universal 15N2-diazirine molecular tags. Sci. Adv. 2, e1501438 (2016). 2 Stevanato, G. et al. A Nuclear Singlet Lifetime of More than One Hour in Room-Temperature Solution. Angew. Chem. Int. Ed. 54, 3740-3743 (2015). You can insert an image with the button on the right:

Domaines

Chimie organique
Fichier non déposé

Dates et versions

hal-01828231 , version 1 (23-07-2018)

Identifiants

  • HAL Id : hal-01828231 , version 1

Citer

Guannan Zhang, Johannes Collel, Vincent Reboul, Thomas Glachet, Warren Warren, et al.. Direct hyperpolarization of 15N2 singlet states in terminal diazirines enables long lived hyperpolarization and sensitive proton detection. European Magnetic Resonance Meeting - EUROMAR, Jul 2018, Nantes, France. ⟨hal-01828231⟩
115 Consultations
1 Téléchargements

Partager

Gmail Facebook X LinkedIn More