Abstract:
:The interactions of the hydrophobic pulmonary surfactant proteins SP-B and SP-C with 1,2-dipalmitoylphosphatidylcholine in mixed, spread monolayer films have been studied in situ at the air/water interface with the technique of external reflection absorption infrared spectroscopy (IRRAS). SP-C has a mostly alpha-helical secondary structure both in the pure state and in the presence of lipids, whereas SP-B secondary structure is a mixture of alpha-helical and disordered forms. When films of SP-B/1,2-dipalmitoylphosphatidylcholine are compressed to surface pressures (pi) greater than approximately 40-43 mN/m, the protein is partially (15-35%) excluded from the surface, as measured by intensity ratios of the peptide bond amide l/lipid C==O stretching vibrations. The extent of exclusion increases as the protein/lipid ratio in the film increases. In contrast, SP-C either remains at the surface at high pressures or leaves accompanied by lipids. The amide l peak of SP-C becomes asymmetric as a result of the formation of intermolecular sheet structures (1615-1630 cm-1) suggestive of peptide aggregation. The power of the IRRAS experiment for determination of film composition and molecular structure, i.e., as a direct test of the squeeze-out hypothesis of pulmonary surfactant function, is evident from this work.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Pastrana-Rios B,Taneva S,Keough KM,Mautone AJ,Mendelsohn Rdoi
10.1016/S0006-3495(95)80124-4subject
Has Abstractpub_date
1995-12-01 00:00:00pages
2531-40issue
6eissn
0006-3495issn
1542-0086pii
S0006-3495(95)80124-4journal_volume
69pub_type
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