Keeping lung surfactant where it belongs: protein regulation of two-dimensional viscosity.
Lung surfactant causes the surface tension, gamma, in the alveoli to drop to nearly zero on exhalation; in the upper airways gamma is approximately 30 mN/m and constant. Hence, a surface tension gradient exists between alveoli and airways that should lead to surfactant flow out of the alveoli and elimination of the surface tension gradient. However, the lung surfactant specific protein SP-C enhances the resistance to surfactant flow by regulating the ratio of solid to fluid phase in the monolayer, leading to a jamming transition at which the monolayer transforms from fluidlike to solidlike. The accompanying three orders of magnitude increase in surface viscosity helps minimize surfactant flow to the airways and likely stabilizes the alveoli against collapse.
Alonso
Coralie
C
Department of Chemical Engineering, University of California, Santa Barbara, California 93106-5080, USA.
Waring
Alan
A
Zasadzinski
Joseph A
JA
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D000818:Animals; D001688:Biological Products / Q000737:chemistry; D001703:Biophysics / Q000379:methods; D002417:Cattle; D008055:Lipids / Q000737:chemistry; D008168:Lung / Q000737:chemistry / Q000378:metabolism*; D008280:Magnetics; D018625:Microscopy, Atomic Force; D010715:Phosphatidylglycerols / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry; D011312:Pressure; D011506:Proteins / Q000737:chemistry*; D011650:Pulmonary Alveoli / Q000378:metabolism; D037721:Pulmonary Surfactant-Associated Protein C / Q000737:chemistry; D011663:Pulmonary Surfactants / Q000737:chemistry; D013499:Surface Properties; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014783:Viscosity
D001688:Biological Products; D008055:Lipids; D010715:Phosphatidylglycerols; D010743:Phospholipids; D011506:Proteins; D037721:Pulmonary Surfactant-Associated Protein C; D011663:Pulmonary Surfactants; D013501:Surface-Active Agents; D015060:1,2-Dipalmitoylphosphatidylcholine; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol; C068291:poractant alfa; C072197:beractant