Several methods of measuring the line tension between phase-separated liquid-ordered-liquid -disordered domains in phospholipid-cholesterol systems have been proposed. These experimental techniques are typically internally self-consistent, but the measured line tension values vary widely among these techniques. To date, no measurement of line tension has utilized multiple experimental techniques to look at the same monolayer system. Here we compare two nonperturbative methods, Fourier analysis of boundary fluctuations (BA) and one proposed by Israelachvili involving the analysis of domain size distributions (SD), to extract the line tension in a 70 mol % DMPC/30 mol % dihydrocholesterol (DChol) mixture as a function of surface pressure. We show that BA predicts the expected variation in line tension measurements consistent with the theoretical critical exponent whereas SD does not. From this comparison, we conclude that the size distribution of monolayer domains is metastable and primarily determined by the kinetics of domain nucleation and subsequent aging.
Bibliographical noteFunding Information:
We thank Ravi Tavakley and members of Augsburg Biophysics. We thank Emil Eldo and Promise Okeke for preliminary experiments performed in support of this project. Research in Augsburg’s biophysics laboratory is supported by the National Science Foundation: DMR 1207544 and MRI 1040126. We thank Dixie Shafer, Kirsten O’Brien, and Augsburg University’s Office of Undergraduate Research and Graduate Opportunities. Undergraduate researchers acknowledge the support of summer research stipends from Dean and Amy Sundquist. J.A.Z. and B.L.S. were partially supported by National Institutes of Health grants HL 51177 and HL 135065 and NSF grant CBET 1706378.
© 2019 American Chemical Society.