title: Effect of hydrophobic surfactant proteins SP-B and SP-C on binary phospholipid monolayers: II. Infrared external reflectance-absorption spectroscopy.
abstract: In situ external reflection infrared spectroscopy at the air-water interface was used to study the influence on phospholipid structure of an endogenous mixture of the two hydrophobic surfactant proteins, SP-B and SP-C, which are thought to play pivotal roles in the adsorption and function of pulmonary surfactant. Mixtures studied were 1:1, 2:1, and 7:1 (mol:mol) DPPC-d(62):DPPG, and 7:1 DPPC-d(62):DOPG, alone and in the presence of 0.5-10 wt % mixed SP-B/C purified chromatographically from calf lung surfactant extract. Perdeuteration of DPPC produced a shift in vibrational frequencies so that it could be differentiated spectroscopically from the phosphoglycerol component in the surface monolayer. CH(2) antisymmetric and symmetric stretching bands ( approximately 2920 and 2852 cm(-1)) along with the analogous CD(2) stretching bands ( approximately 2194 and 2089 cm(-1)) were analyzed, and band heights and peak wavenumber positions were assessed as a function of monolayer surface pressure. Small, near-physiological contents of 1-2 wt % SP-B/C typically produced the maximum observed spectroscopic effects, which were abolished at high protein contents of 10 wt %. Analysis of CH(2) and CD(2) stretching bands and C-H/C-D band height ratios indicated that SP-B/C affected PC and PG lipids differently within the surface monolayer. SP-B/C had preferential interactions with DPPG in 1:1, 2:1, and 7:1 DPPC-d(62):DPPG films that increased its acyl chain order. SP-B/C also interacted specifically with DOPG in 7:1 DPPC-d(62):DOPG monolayers, but in this case an increase in CH(2) band heights and peak wavenumber positions indicated a further disordering of the already fluid DOPG acyl chains. CD(2) band height and peak wavenumber analysis indicated that SP-B/C had no significant effect on the structure of DPPC-d(62) chains in 7:1 films with DPPG or DOPG, and had only a slight tendency to increase the acyl chain order in 1:1 films of DPPC-d(62):DPPG. SP-B/C had no significant effect on DPPC-d(62) structure in films with DOPG. Infrared results also indicated that interactions involving SP-B/C and lipids led to exclusion of PC and PG lipids from the compressed interfacial monolayer, in agreement with our previous report on the phase morphology of lipid monolayers containing 1 wt % SP-B/C.
authors.affiliation: Department of Chemistry, University of Georgia, Athens 30602, USA.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Brockman
authors.forename: Zhengdong
authors.initials: Z
authors.lastname: Wang
authors.forename: Robert H
authors.initials: RH
authors.lastname: Notter
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dluhy
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008560:Membrane Fluidity; D008567:Membranes, Artificial; D008968:Molecular Conformation; D010715:Phosphatidylglycerols / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D011312:Pressure; D011485:Protein Binding; D037701:Pulmonary Surfactant-Associated Protein B / Q000737:chemistry*; D037721:Pulmonary Surfactant-Associated Protein C / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013499:Surface Properties; D013500:Surface Tension
chemical_list: D008567:Membranes, Artificial; D010715:Phosphatidylglycerols; D010743:Phospholipids; D037701:Pulmonary Surfactant-Associated Protein B; D037721:Pulmonary Surfactant-Associated Protein C; D015060:1,2-Dipalmitoylphosphatidylcholine; C051388:1,2-dioleoyl-sn-glycero-3-phosphoglycerol; C030345:1,2-dipalmitoylphosphatidylglycerol