Biophysical characterization and modeling of lung surfactant components

Abstract

The present study characterizes the dynamic interfacial properties of calf lung surfactant (CLS) and samples reconstituted in a stepwise fashion from phospholipid (PL), hydrophobic apoprotein (HA), surfactant apoprotein A (SP-A), and neutral lipid fractions. Dipalmitoylphosphatidylcholine (DPPC), the major PL component of surfactant, was examined for comparison. Surface tension was measured over a range of oscillation frequencies (1-100 cycles/min) and bulk phase concentrations (0.01-1 mg/ml) by using a pulsating bubble surfactometer. Distinct differences in behavior were seen between samples. These differences were interpreted by using a previously validated model of surfactant adsorption kinetics that describes function in terms of 1) adsorption rate coefficient (k1), 2) desorption rate coefficient (k2), 3) minimum equilibrium surface tension (γ*), 4) minimum surface tension at film collapse (γ(min)), and 5) change in surface tension with interfacial area for γ