Simple expressions of the nuclear relaxation rate enhancement due to quadrupole nuclei in slowly tumbling molecules - Archive ouverte HAL Access content directly
Journal Articles The Journal of Chemical Physics Year : 2015

Simple expressions of the nuclear relaxation rate enhancement due to quadrupole nuclei in slowly tumbling molecules

Abstract

For slowly tumbling entities or quasi-rigid lattices, we derive very simple analytical expressions of the quadrupole relaxation enhancement (QRE) of the longitudinal relaxation rate R1 of nuclear spins I due to their intramolecular magnetic dipolar coupling with quadrupole nuclei of arbitrary spins S 1. These expressions are obtained by using the adiabatic approximation for evaluating the time evolution operator of the quantum states of the quadrupole nuclei S. They are valid when the gyromagnetic ratio of the spin S is much smaller than that of the spin I. The theory predicts quadrupole resonant peaks in the dispersion curve of R1 vs magnetic field. The number, positions, relative intensities, Lorentzian shapes, and widths of these peaks are explained in terms of the following properties: the magnitude of the quadrupole Hamiltonian and the asymmetry parameter of the electric field gradient (EFG) acting on the spin S, the S-I inter-spin orientation with respect to the EFG principal axes, the rotational correlation time of the entity carrying the S I pair, and/or the proper relaxation time of the spin S. The theory is first applied to protein amide protons undergoing dipolar coupling with fast-relaxing quadrupole N-14 nuclei and mediating the QRE to the observed bulk water protons. The theoretical QRE agrees well with its experimental counterpart for various systems such as bovine pancreatic trypsin inhibitor and cartilages. The anomalous behaviour of the relaxation rate of protons in synthetic aluminium silicate imogolite nano-tubes due to the QRE of 27A1 (S = 5/2) nuclei is also explained. (C) 2015 AIP Publishing LLC.
No file

Dates and versions

hal-01592972 , version 1 (25-09-2017)

Identifiers

Cite

Pascal H. Fries, Elie Belorizky. Simple expressions of the nuclear relaxation rate enhancement due to quadrupole nuclei in slowly tumbling molecules. The Journal of Chemical Physics, 2015, 143 (4), pp.044202. ⟨10.1063/1.4926827⟩. ⟨hal-01592972⟩
171 View
0 Download

Altmetric

Share

Gmail Mastodon Facebook X LinkedIn More