Nuclear spin relaxation of sodium cations in bacteriophage Pf1 solutions

Abstract

The nuclear magnetic resonance (NMR) spectra for the I=3/2 23Na cation dissolved into filamentous bacteriophage Pf1 solutions display line splittings and relaxation times consistent with an interaction between the 23Na nuclear quadrupole moment and the electric field gradient produced by the negatively charged Pf1 particles. The 23Na NMR line splittings and relaxation rates corresponding to magnetization recovery and single, double, and triple quantum coherence decays are measured in Pf1 solutions and compared to theoretical values. The deviation of the observed dc spectral density J0 from the equal first harmonic J(omega0) and second harmonic J(2omega0) values as J(omega0)=J(2omega0) not equal to J0 in these solutions suggests that ion migration in the electric field gradient of the Pf1 particles produces an anisotropic relaxation mechanism. Correlation functions and thus spectral densities for this process are calculated from solutions to the Fokker-Planck equation for radial motion in an electric potential and used to estimate measured relaxation rates. Appropriate electric potentials are generated from the solutions to the Poisson-Boltzmann equation for a charged Pf1 particle in aqueous phase, functions that lead to theoretical estimates of NMR line splittings consistent with experimental observations.

z-Spectra of 23Na+ in stretched gels: Quantitative multiple quantum analysis

“…However, when fitting the z-spectra using only the Js (Fig. 3) without constraints yielded the outcome that J 1 < J 2 ; this is physically impossible for a system that is fastmotionally averaged; but there are situations involving, diffusion on curved surfaces [38], and ion migration in an electric field gradient of a virus particle for which J 1 < J 2 [39]. In another biological case, bovine nasal cartilage, the inequality is not apparent, but nevertheless J 1 = J 2 [40].…”

Dynamics of $I = {3 \over 2}$ nuclei in isotropic slow motion, anisotropic and partially ordered phases

“…As to be expected, and reported by Augustine and coworkers, the isotropic diffusion model may not adequately represent the motional characteristics in this sample (32,35). Additionally, the presence of splittings in the frequency dimensions of all IR and the STA data and the very existence of the 2nd rank STA spectrum, indicate the presence of nonzero residual quadrupole coupling, constituting compelling evidence for anisotropic diffusion.…”

“…Once again it is worth stressing here that (see (Eqs. [33][34][35]41]), the STA signal during τ contains both oscillatory and dissipative terms.…”

Quadrupole sensitive pulse for signal filtering

“…This is an indication that biexponential relaxation, where the central and satellite transitions have different relaxation times T 2,CT and T 2,ST is the reason for the observed effects (Fig. 12c) 31 :. The central transition of the first order Hamiltonian does not depend on the quadrupolar frequency and therefore the dependence of CT on ν Q occurs because of appearance satellite transitions during the QSP, which contribute to the value of CT .…”