Critical fluctuations in DOPC/DPPC-d62/cholesterol mixtures: 2H magnetic resonance and relaxation

Static and magic angle spinning (MAS) (2)H nuclear magnetic resonance experiments have been performed on a series of multilamellar dispersions of di-oleoyl-sn-glycero-3-phosphocholine/di-palmitoyl-sn-glycero-3-phosphocholine-d62/cholesterol in water to investigate the compositional fluctuations which occur in the region of the line of critical points for this ternary system. The strong dependence of the MAS line widths on temperature, sample composition, and spinning rate provides a direct measure of the magnitude of the fluctuations in the (2)H quadrupolar Hamiltonian. These data are analyzed in terms of models for critical fluctuations in composition leading to a value for the critical index for the correlation length, ν(c) = 0.628, consistent with a three dimensional Ising model.