Effect of hydrophobic surfactant peptides SP-B and SP-C on binary phospholipid monolayers. I. Fluorescence and dark-field microscopy

Academic Article

Abstract

  • The influence of the hydrophobic proteins SP-B and SP-C, isolated from pulmonary surfactant, on the morphology of binary monomolecular lipid films containing phosphocholine and phosphoglycerol (DPPC and DPPG) at the air- water interface has been studied using epifluorescence and dark-field microscopy. In contrast to previously published studies, the monolayer experiments used the entire hydrophobic surfactant protein fraction (containing both the SP-B and SP-C peptides) at physiologically relevant concentrations (~1 wt %). Even at such low levels, the SP-B/C peptides induce the formation of a new phase in the surface monolayer that is of lower intrinsic order than the liquid condensed (LC) phase that forms in the pure lipid mixture. This presumably leads to a higher structural flexibility of the surface monolayer at high lateral pressure. Variation of the subphase pH indicates that electrostatic interaction dominates the association of the SP- B/C peptides with the lipid monolayer. As evidenced from dark-field microscopy, monolayer material is excluded from the DPPC/DPPG surface film on compression and forms three-dimensional, surface-associated structures of micron dimensions. Such exclusion bodies formed only with SP-B/C peptides. This observation provides the first direct optical evidence for the squeeze- out of pulmonary surfactant material in situ at the air-water interface upon increasing monolayer surface pressures.
  • Authors

    Published In

    Digital Object Identifier (doi)

    Pubmed Id

  • 22753902
  • Author List

  • Krüger P; Schalke M; Wang Z; Notter RH; Dluhy RA; Lösche M
  • Start Page

  • 903
  • End Page

  • 914
  • Volume

  • 77
  • Issue

  • 2