Issue 40, 2019

Experimental evidence for the role of paramagnetic oxygen concentration on the decay of long-lived nuclear spin order

Abstract

Nuclear singlet lifetimes are often dependent on the quantity of paramagnetic oxygen species present in solution, although the extent to which quenching or removing molecular oxygen has on extending singlet lifetimes is typically an unknown factor. Here we investigate the behaviour of the singlet relaxation time constant as a function of the oxygen concentration in solution. An experimental demonstration is presented for a chemically inequivalent proton pair of the tripeptide alanine–glycine–glycine in solution. We introduce a simple methodology to ensure the solution is saturated with predetermined concentrations of oxygen gas prior to measurements of the singlet lifetime. Singlet lifetimes were measured by using the spin-lock induced crossing pulse sequence. We present a linear relationship between the amount of oxygen dissolved in solution and the singlet relaxation rate constant. Singlet relaxation was found to be ∼2.7 times less sensitive to relaxation induced by paramagnetic oxygen compared with longitudinal relaxation. The relaxation behaviour is described by using a model of correlated fluctuating fields. We additionally examine the extension of singlet lifetimes by doping solutions with the chelating agent sodium ascorbate, which scavenges oxygen radicals in solution.

Graphical abstract: Experimental evidence for the role of paramagnetic oxygen concentration on the decay of long-lived nuclear spin order

Supplementary files

Article information

Article type
Paper
Submitted
18 May 2019
Accepted
09 Jul 2019
First published
29 Jul 2019
This article is Open Access
Creative Commons BY license

RSC Adv., 2019,9, 23418-23424

Experimental evidence for the role of paramagnetic oxygen concentration on the decay of long-lived nuclear spin order

B. Erriah and S. J. Elliott, RSC Adv., 2019, 9, 23418 DOI: 10.1039/C9RA03748A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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