Polar Interactions Play an Important Role in the Energetics of the Main Phase Transition of Phosphatidylcholine Membranes

Garcia, A; Zou, H; Hossain, KR; Xu, QH; Buda, A; Clarke, RJ

Polar Interactions Play an Important Role in the Energetics of the Main Phase Transition of Phosphatidylcholine Membranes

Garcia, A

Zou, H Hossain, KR

Xu, QH Buda, A Clarke, RJ

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Publication Type:: Journal Article
Citation:: ACS Omega, 2019, 4 (1), pp. 518 - 527
Issue Date:: 2019-01-08

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Field	Value	Language
dc.contributor.author	Garcia, A https://orcid.org/0000-0002-1159-4567	en_US
dc.contributor.author	Zou, H	en_US
dc.contributor.author	Hossain, KR https://orcid.org/0000-0003-4506-1491	en_US
dc.contributor.author	Xu, QH	en_US
dc.contributor.author	Buda, A	en_US
dc.contributor.author	Clarke, RJ	en_US
dc.date.available	2018-12-26	en_US
dc.date.issued	2019-01-08	en_US
dc.identifier.citation	ACS Omega, 2019, 4 (1), pp. 518 - 527	en_US
dc.identifier.uri	http://hdl.handle.net/10453/136261
dc.description.abstract	© 2019 American Chemical Society. Conformational changes of membrane proteins are accompanied by deformation in the surrounding lipid bilayer. To gain insight into the energetics of membrane deformation, the phase behavior of dimyristoylphosphatidylcholine (DMPC) membranes in the presence of the dipole potential, d, modifiers was investigated by differential scanning calorimetry. 7-Ketocholesterol, which weakens d and reduces membrane-perpendicular dipole-dipole repulsion, causes a discrete second peak on the high-temperature side of the main transition, whereas 6-ketocholestanol, which strengthens d and increases membrane-perpendicular dipole-dipole repulsion, merely produces a shoulder. Measurements on pure DMPC vesicles showed that the observed temperature profile could not be explained by a single endothermic process, that is, breaking of van der Waals forces between hydrocarbon chains alone. Removal of NaCl from the buffer caused an increase in the main transition temperature and the appearance of an obvious shoulder, implicating polar interactions. Consideration of the phosphatidylcholine (PC) head group dipole moment indicates direct interactions between PC dipoles that are unlikely to account for the additional process. It seems more likely that the breaking of an in-plane hydrogen-bonded network consisting of hydrating water dipoles together with zwitterionic lipid head groups is responsible. The evidence presented supports the idea that the breaking of van der Waals forces between lipid tails required for the main phase transition of PC membranes is coupled to partial breaking of a hydrogen-bonded network at the membrane surface.	en_US
dc.relation.ispartof	ACS Omega	en_US
dc.relation.isbasedon	10.1021/acsomega.8b03102	en_US
dc.title	Polar Interactions Play an Important Role in the Energetics of the Main Phase Transition of Phosphatidylcholine Membranes	en_US
dc.type	Journal Article
utslib.citation.volume	1	en_US
utslib.citation.volume	4	en_US
utslib.for	0904 Chemical Engineering	en_US
utslib.for	0912 Materials Engineering	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Life Sciences
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences
utslib.copyright.status	open_access
pubs.issue	1	en_US
pubs.publication-status	Published	en_US
pubs.volume	4	en_US

Abstract:

© 2019 American Chemical Society. Conformational changes of membrane proteins are accompanied by deformation in the surrounding lipid bilayer. To gain insight into the energetics of membrane deformation, the phase behavior of dimyristoylphosphatidylcholine (DMPC) membranes in the presence of the dipole potential, d, modifiers was investigated by differential scanning calorimetry. 7-Ketocholesterol, which weakens d and reduces membrane-perpendicular dipole-dipole repulsion, causes a discrete second peak on the high-temperature side of the main transition, whereas 6-ketocholestanol, which strengthens d and increases membrane-perpendicular dipole-dipole repulsion, merely produces a shoulder. Measurements on pure DMPC vesicles showed that the observed temperature profile could not be explained by a single endothermic process, that is, breaking of van der Waals forces between hydrocarbon chains alone. Removal of NaCl from the buffer caused an increase in the main transition temperature and the appearance of an obvious shoulder, implicating polar interactions. Consideration of the phosphatidylcholine (PC) head group dipole moment indicates direct interactions between PC dipoles that are unlikely to account for the additional process. It seems more likely that the breaking of an in-plane hydrogen-bonded network consisting of hydrating water dipoles together with zwitterionic lipid head groups is responsible. The evidence presented supports the idea that the breaking of van der Waals forces between lipid tails required for the main phase transition of PC membranes is coupled to partial breaking of a hydrogen-bonded network at the membrane surface.

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http://hdl.handle.net/10453/136261