Department of Chemical Engineering, University of Kansas, Lawrence, Kansas, USA.
Biophys J. 2012 Jan 4;102(1):56-65. doi: 10.1016/j.bpj.2011.11.4007. Epub 2012 Jan 3.
The size distribution of domains in phase-separated lung surfactant monolayers influences monolayer viscoelasticity and compressibility which, in turn, influence monolayer collapse and set the compression at which the minimum surface tension is reached. The surfactant-specific protein SP-B decreases the mean domain size and polydispersity as shown by fluorescence microscopy. From the images, the line tension and dipole density difference are determined by comparing the measured size distributions with a theory derived by minimizing the free energy associated with the domain energy and mixing entropy. We find that SP-B increases the line tension, dipole density difference, and the compressibility modulus at surface pressures up to the squeeze-out pressure. The increase in line tension due to SP-B indicates the protein avoids domain boundaries due to its solubility in the more fluid regions of the film.
在相分离的肺表面活性剂单层中，畴的大小分布会影响单层的粘弹性和可压缩性，而这反过来又会影响单层的塌陷，从而确定达到最小表面张力时的压缩程度。荧光显微镜显示，表面活性物质特异性蛋白 SP-B 会减小平均畴尺寸和多分散性。通过将测量的尺寸分布与通过最小化与畴能量和混合熵相关的自由能得出的理论进行比较，从图像中确定了线张力和偶极密度差。我们发现，SP-B 会增加线张力、偶极密度差以及表面压高达挤压压力时的压缩模量。SP-B 引起的线张力增加表明，由于其在膜的更流动区域中的溶解度，该蛋白质避免了畴边界。
