Effect of a Bovine Lung Surfactant Protein Isolate (SP-B/C) on Egg Phosphatidylglycerol Acyl Chain Order in a Lipid Mixture with Dipalmitoylphosphatidylcholine and Palmitic Acid

Abstract

Dynamic surface tension measurements of films of a d621,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine:L-α-phosphatidyl-DL-glycerol:d31palmitic acid (d62-DPPC:EggPG:d31-PA) lipid matrix in the presence of a bovine pulmonary surfactant protein isolate (SP-B/C) demonstrate the improved surface activity over that of the lipids alone. Thus, significant interaction of the proteins with the lipid matrix is demonstrated. The effect of SP-B/C on the acyl chain order of the negatively charged EggPG within a d62-DPPC:EggPG:d31-PA lipid matrix in D2O saline was investigated in thermal perturbation Fourier transform IR spectroscopic studies. The EggPG thermotropic phase behavior was determined independently of the other lipid components with perdeuterated lipids and D2O. The data demonstrate the high degree of EggPG acyl chain disorder in the absence of the protein isolate. A broad transition occurs between 30 and 40 °C. The addition of the protein isolate did not alter the acyl chain order at 0.281 and 1.46 mg/mL of protein. However, alterations in the lipid carbonyl vibrational mode were observed.