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Interactions of pulmonary surfactant protein a with phospholipid monolayers change with ph.
| Content Provider | CiteSeerX |
|---|---|
| Abstract | ABSTRACT The interaction of pulmonary surfactant protein A (SP-A) labeled with Texas Red (TR-SP-A) with monolayers containing zwitterionic and acidic phospholipids has been studied at pH 7.4 and 4.5 using epifluorescence microscopy. At pH 7.4, TR-SP-A expanded the p-A isotherms of film of dipalmitoylphosphatidylcholine (DPPC). It interacted at high concentration at the edges of condensed-expanded phase domains, and distributed evenly at lower concentration into the fluid phase with increasing pressure. At pH 4.5, TR-SP-A expanded DPPC monolayers to a slightly lower extent than at pH 7.4. It interacted primarily at the phase boundaries but it did not distribute into the fluid phase with increasing pressure. Films of DPPC/dipalmitoylphosphatidylglycerol (DPPG) 7:3 mol/mol were somewhat expanded by TR-SP-A at pH 7.4. The protein was distributed in aggregates only at the condensed-expanded phase boundaries at all surface pressures. At pH 4.5 TR-SP-A caused no expansion of the p-A isotherm of DPPC/DPPG, but its fluorescence was relatively homogeneously distributed throughout the expanded phase at all pressures studied. These observations can be explained by a combination of factors including the preference for SP-A aggregates to enter monolayers at packing dislocations and their disaggregation in the presence of lipid under increasing pressure, together with the influence of pH on the aggregation state of SP-A and the interaction of SP-A with zwitterionic and acidic lipid. |
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| Access Restriction | Open |
| Subject Keyword | Pulmonary Surfactant Protein Phospholipid Monolayers Change P-a Isotherm Fluid Phase Acidic Lipid Dppc Dipalmitoylphosphatidylglycerol Sp-a Aggregate Acidic Phospholipid Mol Mol Dppc Dppg High Concentration Dppc Monolayers Surface Pressure Phase Boundary Epifluorescence Microscopy Aggregation State Condensed-expanded Phase Domain Expanded Phase Condensed-expanded Phase Boundary Texas Red |
| Content Type | Text |
