Spin lattice relaxation of dipole nuclei (I= 1/2) coupled to quadrupole nuclei (S= 1)

Abstract

Nuclear magnetic relaxation has been investigated for dipole nuclei (I = 1/2) coupled to quadrupole nuclei (S = 1) by dipolar interaction. Quadrupole dips in the frequency dependence of the longitudinal relaxation time of the I-spins are predicted under certain conditions. Relaxation dispersion experiments have been performed with Bovine Serum Albumin, which contains ¹⁴N¹H-groups as representatives of the envisaged class of two-spin systems. In the dry and hydrated protein, quadrupole dips have been observed. The conclusion is that near room temperature and up to frequencies of the order of at least 10⁷ Hz the ¹⁴H¹H-groups are the dominant relaxation centres. The relevance for investigations of other biological systems is briefly discussed.