PHASE AND MORPHOLOGY CHANGES IN LIPID MONOLAYERS INDUCED BY SP-B PROTEIN AND ITS AMINO-TERMINAL PEPTIDE

Both human lung surfactant protein, SP-B, and its amino-terminal pepti de, SP-B-1-25, inhibit the formation of condensed phases in monolayers of palmitic acid, resulting new fluid phase. This fluid phase forms a network, separating condensed-phase domains at coexistence. The netwo rk persists to high surface pressures, altering the nucleation, growth , and morphology of monolayer collapse structures, leading to lower su rface tensions on compression and more reversible respreading on expan sion. The network is stabilized by the low line tension between the fl uid phase and the condensed phase as confirmed by the formation of ''s tripe'' phases.