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. 2005 Apr 15;89(1):266–273. doi: 10.1529/biophysj.104.052092

FIGURE 8.

FIGURE 8

Surface shear viscosity of Survanta (bovine lung extract supplemented with DPPC and PA) and Curosurf (porcine lung extract) replacement lung surfactants. Both show similar behavior to the lipid mixtures in that the surface viscosity strongly increases at a surface pressure (our magnetic needle surface viscometer can only measure up to ∼50 mN/m) corresponding to an SP-C induced percolation of the solid phase domains in the monolayer. Survanta has a lower transition surface pressure than Curosurf at 25°C, as the added PA and DPPC in Survanta increase the solid phase fraction as in Fig. 1 (inset). Raising the temperature of the Survanta film to 37° moves the transition to higher surface pressure, consistent with the observation that the solid phase fraction is smaller at higher temperatures (13,34). Raising the temperature of the Curosurf film to 37° presumably moves the transition to a surface pressure higher than could be measured using the magnetic needle viscometer (data not shown).