(a) Nitrogen hyperfine spacing A+ of 0.2 mM TEMPO-stearate in the presence of 100 mM of phospholipids in Hepes buffer equilibrated with N2 at pH 7.4 (left-hand ordinate) and corresponding effective water concentration [H2O] in the polar shell calculated from Eq. (1) (right-hand ordinate) as a function of temperature. Symbols used to identify the different lysophospholipid-phospholipid concentrations in mixed DMPG-LMPC vesicles are: (○) 20 mM LMPC, 80 mM DMPG; (□) 10 mM LMPC, 90 mM DMPG; (◇) 5 mM LMPC, 95 mM DMPG; (△) 4 mM LMPC, 96 mM DMPG; (▽) 3.5 mM LMPC, 96.5 mM DMPG; (▷) 2 mM LMPC, 98 mM DMPG; (●) 100 mM DMPG (DMPG vesicles) and (■) 100 mM LMPC (LMPC micelles). Error bars are standard deviations of five measurements. Lines are to guide the eyes.