Title

Monolayer coupling in phosphatidylserine bilayers: Distinct phase transitions induced by magnesium interacting with one or both monolayers

ORCiD

Nejat Düzgüneş: 0000-0001-6159-1391

Document Type

Article

Publication Title

Biochimica et Biophysica Acta - Biomembranes

ISSN

0005-2736

Volume

944

Issue

3

DOI

10.1016/0005-2736(88)90510-X

First Page

391

Last Page

398

Publication Date

10-20-1988

Abstract

We have investigated the thermotropic behavior of phosphatidylserine bilayers interacting with Mg2+ either on one side or both sides, using differential scanning calorimetry. Large unilamellar vesicles (LUV) of phosphatidylserine exposed to Mg2+ on the external side only displayed an upward shift of the gel-liquid transition temperature (Tm) of about 6-8 C° relative to the Tm of LUV in Na+. Mg2+ was shown not to enter the vesicle interior, by means of fluorescence measurements on encapsulated 8-hydroxyquinoline-5-sulfonate. Multilamellar vesicles prepared in the presence of Mg2+, or vesicles prepared by Mg2+-induced fusion of small unilamellar vesicles, had Tm values that were shifted upward by about 16-17 C°. When the latter preparation was treated with EDTA to produce vesicles with Mg2+ inside and Na+ outside, the Tm was found to be shifted again by only 6-8 C°. These observations indicate that the monolayer interacting with Na+ fluidizes the monolayer interacting with Mg2+, and thet the latter tends to solidify the former. The two monolayers thus appear to be coupled, possibly by hydrocarbon chain interdigitation. © 1988.

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