External reflection absorption infrared spectroscopy study of lung surfactant proteins SP-B and SP-C in phospholipid monolayers at the air/water interface.
Biophys J
; 69(6): 2531-40, 1995 Dec.
Article
em En
| MEDLINE
| ID: mdl-8599660
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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteolipídeos
/
1,2-Dipalmitoilfosfatidilcolina
/
Surfactantes Pulmonares
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Estrutura Secundária de Proteína
/
Lipossomos
Limite:
Animals
Idioma:
En
Revista:
Biophys J
Ano de publicação:
1995
Tipo de documento:
Article
País de afiliação:
Estados Unidos