Figure 1.

DMPC membrane structural transformations induced by PG-1’s line-active behavior. (A) In the absence of PG-1, the bilayer was compact and nearly circular with a smooth and minimized edge. (B) Introduction of 0.050 μM PG-1 caused the bilayer to extend and become roughened, and this remained stable over time. Line sections (dashed white lines) of the bilayer before and after the introduction of 0.050 μM PG-1 showed that the lamellar core remained unaffected, and that PG-1 adsorption at the curved edge resulted in a reduction in the bilayer line tension. (C) With increasing bulk PG-1 concentrations, the lamellar organization of the bilayer was compromised by 0.70 μM PG-1, with the formation of worm-like micelles. Peptide insertion thinned the membrane considerably (by ∼1 nm). To better reveal the bilayer’s transformation in (C), the height data were rescaled to a 5 nm range. The dashed box in (C) indicates a zoomed-in region (500 × 500 nm²) that is shown in (C′). (D) A shape factor analysis of the bilayer morphology (S) as a function of the bulk PG-1 concentration showed that PG-1 had a considerable effect in promoting extended morphologies with increased perimeter lengths beyond initial values near S = 1. Error bars in (D) are SDs from at least three replicate bilayer monitoring experiments. All images were obtained at 30°C. White scale bars are 500 nm unless otherwise indicated. To see this figure in color, go online.