Figure 3. Manipulation of the delay time for crystallization at 37°C.

(a) Average delay time increases with the addition of DLPG. Lipid dispersions in buffer containing 150 mM monovalent salt. The last point did not recrystallize in the duration of the experiment (200 hours). (b) Non-monotonic effect of salt concentration on the delay time, τ. With the addition of salt, at low concentrations (<150 mM), τ decreases in a linear fashion (red line), while at high concentrations (>300 mM), there is an order of magnitude increase. (c) Effect of the monensin ionophore on the delay time. Control sample recrystallized at τ = 44.7 hours. The addition of monensin accelerates recrystallization; sample containing 1 mole % monensin:sodium recrystallized with τ = 13.6 hours. Experiments performed on samples containing 90:10 DLPE:DLPG at 150 mM monovalent salt. (d) Consecutive heating-cooling cycles display a prolongation of the delay time accompanied by a decrease in the metastable lamellar scattering intensity. The curves represent the intensity of lamellar (001) scattering from the moment the temperature is brought back to 37°C after heating. Roman numbers indicate the measurement sequence. Inset shows qualitative analysis of the two effects. (b and d) represent data of 95:5 DLPE:DLPG (mole %). Error bars represent the average phase transition time <τ*>.