Chung J, Yu S H, Whitsett J A, Harding P G, Possmayer F
Department of Biochemistry, University of Western Ontario, London, Canada.
Biochim Biophys Acta. 1989 Apr 26;1002(3):348-58. doi: 10.1016/0005-2760(89)90349-4.
The properties of natural bovine surfactant and its lipid extract have been examined with a pulsating bubble surfactometer which assesses the ability of surfactant lipids to adsorb to the air/liquid interface and reduce the surface tension to near 0 dynes/cm during dynamic compression. Studies conducted at 1 mg/ml phospholipid revealed that the surface activity (i.e., the ability to produce low surface tensions) of lipid extracts could be enhanced by incubating the sample at 37 degrees C for 120 min or by addition of CaCl2. In contrast, incubation at 37 degrees C only slightly improved the biophysical activity of natural surfactant and the addition of CaCl2 had a more modest effect than with lipid extracts. With 20 mM CaCl2, the surfactant activity of lipid extract surfactant was similar to that of natural surfactant. Incubation with EDTA reduced the biophysical activity of natural surfactant. Experiments in which increasing amounts of lipid extract were replaced by natural surfactant revealed that small amounts of natural surfactant enhanced the surfactant activity of lipid extract. The biophysical activity of lipid extract surfactant was also increased by the addition of soluble surfactant-associated protein-A (SP-A) (28-36 kDa) purified from natural bovine surfactant. These results indicate that SP-A (28-36 kDa) improves the surfactant activity of lipid extracts by enhancing the rate of adsorption and/or spreading of phospholipid at the air/liquid interface resulting in the formation of a stable lipid monolayer at lower bulk concentrations of either phospholipid or calcium.
已使用脉动气泡表面张力测定仪检测了天然牛肺表面活性剂及其脂质提取物的特性，该仪器可评估表面活性剂脂质在动态压缩过程中吸附到气/液界面并将表面张力降低至接近0达因/厘米的能力。在磷脂浓度为1毫克/毫升的条件下进行的研究表明，通过将样品在37摄氏度下孵育120分钟或添加氯化钙，可以提高脂质提取物的表面活性（即产生低表面张力的能力）。相比之下，在37摄氏度下孵育只能略微改善天然表面活性剂的生物物理活性，并且氯化钙的添加对其的影响比对脂质提取物的影响更为有限。添加20毫摩尔氯化钙后，脂质提取物表面活性剂的表面活性与天然表面活性剂相似。用乙二胺四乙酸（EDTA）孵育会降低天然表面活性剂的生物物理活性。用天然表面活性剂替代越来越多的脂质提取物的实验表明，少量天然表面活性剂可增强脂质提取物的表面活性。从天然牛肺表面活性剂中纯化的可溶性表面活性剂相关蛋白-A（SP-A，28 - 36千道尔顿）的添加也提高了脂质提取物表面活性剂的生物物理活性。这些结果表明，SP-A（28 - 36千道尔顿）通过提高磷脂在气/液界面的吸附和/或铺展速率，从而在磷脂或钙的本体浓度较低时形成稳定的脂质单分子层，进而改善了脂质提取物的表面活性。
