| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 97 === The effects of bovine serum albumin (BSA) on the mixed dipalmitoyl phosphatidylcholine (DPPC)/1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG) (3:1) monolayer behavior at cyclic air/liquid interfaces were investigated by infrared reflection-absorption spectroscopy (IRRAS). The νa-CH2 reflection-absorbance (RA) intensity-relative area and surface pressure-relative area hysteresis curves of adsorbed BSA layers with spread DPPC molecules at air/liquid interfaces revealed that BSA molecules were expelled from interfaces as the DPPC molecules were compressed to condensed states. The squeezed-out of BSA molecules also induced the loss of free DPPC molecules at interfaces. It was found that the surface pressure was increased during the following interface expansion stage, probably due to the readsorption of the BSA molecules. Furthermore, one could observe in the νa-CH2 wavenumber-relative area hysteresis curves that the free DPPC molecules were always close-packed at expanded interfaces, most likely resulting from the readsorption of BSA molecules. The results suggested that the inhibition of DPPC dynamic surface activity at the interface by BSA was attributed to the decreased number of free DPPC molecules and the competitive adsorption of BSA at the interface. When the BSA concentration in the subphases was lowered from 1000 ppm to 10 ppm, the inhibition phenomena mentioned above then became insignificant.
Base on the νa-CH2 RA intensity-relative area and surface pressure-relative area hysteresis curves of adsorbed BSA layers with spread DPPC/POPG (3:1) molecules at air/liquid interfaces, one could presume that POPG had a higher affinity than DPPC with BSA and was selectively expelled from interfaces with BSA. The behavior of selectively expelled POPG from the interface might explain the decrease in the amount of phosphatidylglycerol and the alteration of the phospholipid composition observed in the lungs of patients with the acute respiratory distress syndrome.
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