HAL Id: jpa-00224297
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Submitted on 1 Jan 1984
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THERMODYNAMIC STUDIES OF
MACROMOLECULAR ASSOCIATIONS AT MEMBRANE WATER INTERFACES
D. Worcester, L. Braganza
To cite this version:
D. Worcester, L. Braganza. THERMODYNAMIC STUDIES OF MACROMOLECULAR ASSOCI-
ATIONS AT MEMBRANE WATER INTERFACES. Journal de Physique Colloques, 1984, 45 (C7),
pp.C7-267-C7-267. �10.1051/jphyscol:1984732�. �jpa-00224297�
JOURNAL DE PHYSIQUE
Colloque C7, suppldment au n09, Tome- 45, septembre 1984 page C7-267
THERMODYNAMIC S T U D I E S OF MACROMOLECULAR ASSOCIATIONS A T MEMBRANE- WATER INTERFACES
D.L. Worcester and L.F. Braganza
I n s t i t u t Max uon Laue-Paul Langevin, 256 X, 38042 Grenoble Cedex, France
The aqueous interface between biological membranes is the site of membrane contact and adhesion. The molecular interactions responsible for membrane adhesion are largely unknown, but must be substantial in order to overcome the electrostatic repulsion of negatively charged membrane surfaces.
We have used neutron diffraction together with thermodynamic variables, particularly hydrostatic pressure, but also temperature, pH, ionic and solvent conditions to study the molecular mechanisms of membrane adhesion in myelin membranes, which are insulative layers of membranes around nerve axons in vertebrates. To maintain myelin, adhesion must occur at both the intracellular and extracellular surfaces of the membranes, which can be identified crystallographically in the diffraction experiments. In addition, there are two different types of myelin, depending on whether it is from the peripheral or central nervous system, so the adhesion at four different surfaces has been studied.
The thermodynamic approach has allowed us to identify the dominant types of interactions at the four surfaces. For three of them, ionic bonding predominates, with basic groups provided by a different protein in each case. Hydrostatic pressure dissociates this ionic bonding due to the smaller volumes of dissociated ions in aqueous media. At the fourth surface, the hydrophobic effect dominates the adhesion mechanism. In all of these cases, it is largely the aqueous environment that controls the equilibrium, and the response to thermodynamic perturbation is best understood in terms of aqueous properties.
Membrane proteins appear to be involved in all four cases of myelin membrane adhesion, but the role of lipids is less clear. Because lipid interfacial response to perturbation by hydrostatic pressure is largely unknown, we have made similar studies of multilamellar lipid vesicles in aqueous dispersion and obtained different results than for myelin membranes.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984732
