Fig. 4.

Increased transverse relaxation rates (R₂) but not longitudinal relaxation rates (R₁) are found in membranes of 1:2 DOPC/DPPC-d₆₂ plus 20% Chol in the vicinity of the miscibility critical point (≈30°C). (a and b) Relaxation rates are measured from ²H nuclei. (c and d) Similar trends in relaxation rates occur in the methylene groups of DOPC measured by ¹H MAS NMR. (e) ²H MAS NMR relaxation measurements also indicate that line-broadening is dominated by increased R₂ values. ( f) Critical features of the acquired static ²H NMR spectrum at 30°C (gray) are reproduced by a simulated spectrum (black) that assumes spectral broadening is dominated by values of R₂ from a, as is described in Materials and Methods.