Lipid-protein interactions alter line tensions and domain size distributions in lung surfactant monolayers.
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.
Department of Chemical Engineering, University of Kansas, Lawrence, Kansas, USA. prajnadhar@ku.edu
Prajnaparamita
P
Dhar
Elizabeth
E
Eck
Jacob N
JN
Israelachvili
Dong Woog
DW
Lee
Younjin
Y
Min
Arun
A
Ramachandran
Alan J
AJ
Waring
Joseph A
JA
Zasadzinski
D003198:Computer Simulation; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D008168:Lung / Q000737:chemistry*; D008956:Models, Chemical; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D037701:Pulmonary Surfactant-Associated Protein B / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
D008055:Lipids; D011506:Proteins; D037701:Pulmonary Surfactant-Associated Protein B; D013501:Surface-Active Agents