Lipid-protein interactions alter line tensions and domain size distributions in lung surfactant monolayers

Prajnaparamita Dhar, Elizabeth Eck, Jacob N. Israelachvili, Dong Woog Lee, Younjin Min, Arun Ramachandran, Alan J. Waring, Joseph A. Zasadzinski

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)56-65
Number of pages10
JournalBiophysical journal
Issue number1
StatePublished - Jan 4 2012

Bibliographical note

Funding Information:
Support for this work comes from National Institutes of Health grants No. HL-092158 and No. ES-015330 (to A.J.W.), grant No. HL-51177 (to P.D., E.E., A.J.W., and J.A.Z.), and grant No. GM-076709 (to Y.M., A.R., D.W.L., J.A.Z., and J.N.I.).


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