Aligning pitch for measurements of the shape of captive bubbles.

The first step required for the determination of surface tension from the shape of a captive bubble is the correct alignment of both the solid support against which the bubble floats and the camera used to record its profile. The solid support should be perpendicular to the gravitationally vertical axis. The camera used to visualize the bubble must be aligned to its axis of symmetry.

Hydrophobic surfactant proteins induce a phosphatidylethanolamine to form cubic phases.

The hydrophobic surfactant proteins SP-B and SP-C promote rapid adsorption of pulmonary surfactant to an air/water interface. Previous evidence suggests that they achieve this effect by facilitating the formation of a rate-limiting negatively curved stalk between the vesicular bilayer and the interface. To determine whether the proteins can alter the curvature of lipid leaflets, we used x-ray diffraction to investigate how the physiological mixture of these proteins affects structures formed by 1-palmitoyl-2-oleoyl phosphatidylethanolamine, which by itself undergoes the lamellar-to-inverse hexagonal phase transition at 71 degrees C.