Pulmonary Surfactant Protein A Interacts with Gel-Like Regions in Monolayers of Pulmonary Surfactant Lipid Extract
| Autor: | Kaushik Nag, Kevin M. W. Keough, Cristina Casals, Nathan H. Rich, Lynn-Ann D. Worthman, Miguel L. F. Ruano, Jesús Pérez-Gil |
|---|---|
| Rok vydání: | 2000 |
| Předmět: |
Pulmonary Surfactant-Associated Proteins
Surface Properties Swine Membrane lipids Proteolipids Analytical chemistry Biophysics Texas Red In Vitro Techniques Biophysical Phenomena chemistry.chemical_compound Membrane Lipids Pulmonary surfactant Phase (matter) Monolayer Pressure Animals Pulmonary Surfactant-Associated Protein A Fluorescent Dyes Chemistry Pulmonary Surfactants Fluorescence 4-Chloro-7-nitrobenzofurazan Microscopy Fluorescence Covalent bond Phosphatidylcholines Gels Research Article |
| Zdroj: | Biophysical Journal. 79(5):2657-2666 |
| ISSN: | 0006-3495 |
| DOI: | 10.1016/s0006-3495(00)76504-0 |
| Popis: | Epifluorescence microscopy was used to investigate the interaction of pulmonary surfactant protein A (SP-A) with spread monolayers of porcine surfactant lipid extract (PSLE) containing 1 mol % fluorescent probe (NBD-PC) spread on a saline subphase (145 mM NaCl, 5 mM Tris-HCl, pH 6.9) containing 0, 0.13, or 0.16 microg/ml SP-A and 0, 1.64, or 5 mM CaCl(2). In the absence of SP-A, no differences were noted in PSLE monolayers in the absence or presence of Ca(2+). Circular probe-excluded (dark) domains were observed against a fluorescent background at low surface pressures (pi approximately 5 mN/m) and the domains grew in size with increasing pi. Above 25 mN/m, the domain size decreased with increasing pi. The amount of observable dark phase was maximal at 18% of the total film area at pi approximately 25 mN/m, then decreased to approximately 3% at pi approximately 40 mN/m. The addition of 0.16 microg/ml SP-A with 0 or 1.64 mM Ca(2+) in the subphase caused an aggregation of dark domains into a loose network, and the total amount of dark phase was increased to approximately 25% between pi of 10-28 mN/m. Monolayer features in the presence of 5 mM Ca(2+) and SP-A were not substantially different from those spread in the absence of SP-A, likely due to a self-association and aggregation of SP-A in the presence of higher concentrations of Ca(2+). PSLE films were spread on a subphase containing 0.16 microg/ml SP-A with covalently bound Texas Red (TR-SP-A). In the absence of Ca(2+), TR-SP-A associated with the reorganized dark phase (as seen with the lipid probe). The presence of 5 mM Ca(2+) resulted in an appearance of TR-SP-A in the fluid phase and of aggregates at the fluid/gel phase boundaries of the monolayers. This study suggests that SP-A associates with PSLE monolayers, particularly with condensed or solid phase lipid, and results in some reorganization of rigid phase lipid in surfactant monolayers. |
| Databáze: | OpenAIRE |
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