Conformational changes in SP-B as a function of surface pressure
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Updated: Aug 31, 2026

High-Pressure NMR Experiments for Detecting Protein Low-Lying Conformational States
Published on: June 29, 2021
Wilfred K Fullagar1, Karen A Aberdeen, David G Bucknall
1School of Molecular and Microbial Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
Abstract:
X-ray reflectivity of bovine and sheep surfactant-associated protein B (SP-B) monolayers is used in conjunction with pressure-area isotherms and protein models to suggest that the protein undergoes changes in its tertiary structure at the air/water interface under the influence of surface pressure, indicating the likely importance of such changes to the phenomena of protein squeeze out as well as lipid exchange between the air-water interface and subphase structures. We describe an algorithm based on the well-established box- or layer-models that greatly assists the fitting of such unknown scattering-length density profiles, and which takes the available instrumental resolution into account. Scattering-length density profiles from neutron reflectivity of bovine SP-B monolayers on aqueous subphases are shown to be consistent with the exchange of a large number of labile protons as well as the inclusion of a significant amount of water, which is partly squeezed out of the protein monolayer at elevated surface pressures.
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