Ordering of alkali halide salts dissolved in bacteriophage Pf1 solutions: A nuclear magnetic resonance study

Abstract

The nuclear magnetic resonance ͑NMR͒ spectra of the Iϭ3/2 monovalent ions 23 Na, 35 Cl, 39 K, and 79 Br for NaCl and KBr dissolved into filamentous bacteriophage Pf1 solutions display line splittings and shifts consistent with an interaction between the nuclear spin and the electric field gradient produced by the Pf1 particles. The average electric field gradient and thus the spectral splitting for ions in the void space between magnetically aligned Pf1 particles is modeled using a numerical solution to the Poisson-Boltzmann equation. An NMR titration experiment in a 57 mg/mL Pf1 solution is used to determine the background Na ϩ ion concentration in solution as 32 mM which compares well with the 31.1 mM negative surface charge on Pf1.

Using Sodium Cation Organization To Study the Phase Behavior of Bicelle Solutions

“…It is not surprising that the solution to the Poisson-Boltzmann equation in oblate spheroidal coordinates reliably estimates the residual quadrupolar coupling ∆ ) 600 Hz in the bicelle phase given the 41 µC/cm 2 surface charge on the bicelle. This approach is, however, limited by the lack of available Sternheimer shielding parameters 14,19 for noncrystalline ionic systems. Future work will include the determination of these values in charged liquid crystalline media.…”

“…A combination of these facts with the well-resolved spectrum in Figure 1 suggests that the splitting ∆ can be calculated by modeling the zwitterionic surface of the bicelles as an oblate spheroidal surface in solution. In analogy to the rodlike polyelectrolytes where the construction of a cell around a charged cylinder has been shown to predict both the nuclear spin relaxation properties 12 and residual quadrupolar splitting of 23 Na in solution, 14 a similar oblate spheroidal surface adapted to the bicelle symmetry can be used to define a cell around a chosen bicelle. As in any coordinate system, there are three variables describing a location in space.…”

“…For this reason, the splitting ∆ in eq 4 was recalculated using the Sternheimer factor of (1 -γ ∞ ) ) 13.25 observed for 23 Na in Pf1 solution. 14 To match theory to experiment the dielectric constant had to be lowered from / 0 ) 80 to / 0 ) 18.5. Such a decrease in dielectric constant is not unreasonable as the very small ≈5.3 zL volume void space between bicelles combined with high ionic strength can disrupt the hydrogen bonding network in bulk water, the property that leads to a high dielectric constant for water.…”

“…It has been long established that the NMR spectra of quadrupolar ions are sensitive to electric field gradients in an anisotropic medium like aqueous phase lamellar liquid crystals. 10 A number of models exist that describe residual quadrupolar effects in these liquid crystalline systems, 10,11 and it is anticipated that solutions to the Poisson-Boltzmann equation that have been successfully applied to the rodlike polyelectrolytes [12][13][14] can be generalized to apply here in the case of the oblate spheroidal phospholipid bicelles.…”

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.…”