Wasserabstossungen zwischen Biomembranen/Hydration repulsion between biomembranes

E. Schneck, F. Sedlmeier and R. R. Netz, PNAS, 109, 14405-9 (2012) / Chemiextra 10/2012

News from Aug 20, 2012

Chemiextra 10/2012: Abstossung zwischen Biomembranen

Biomembranen umhüllen biologische Zelllen wie eine Haut. Sie umschliessen auch die Organellen, die innerhalb der Zelle wichtige Aufgaben beim Stoffwechsel oder der Zellteilung übernehmen. Wie Biomembranen grundsätzlich aufgebaut sind, ist schon lange bekannt. Auch, dass Wassermoleküle benachbarte Biomembranen auf Abstand halten - sonst könnten diese ihre lebenswichtigen Funktionen nicht erfüllen. Mithilfe von Computersimulationen haben Wissenschaftler der TU München und der Freien Universität Berlin jetzt zwei verschiedene Mechanismen entdeckt, die verhindern, dass benachbarte Membran-Oberflächen zusammenkleben. pdf

 

PNAS, 109,14405-9: Hydration repulsion between biomembranes results from an interplay of hydration and depolarization

Hydration repulsion dominates the interaction between polar surfaces in water at nanometer separations and ultimately prevents the sticking together of biological matter. Although confirmed by a multitude of experimental methods for various systems, its mechanism remained unclear. A simulation technique is introduced that yields accurate pressures between solvated surfaces at prescribed water chemical potential and is applied to a stack of phospholipid bilayers. Experimental pressure data are quantitatively reproduced and the simulations unveil a rich microscopic picture: Direct membrane–membrane interactions are attractive but overwhelmed by repulsive indirect water contributions. Below about 17 water molecules per lipid, this indirect repulsion is of an energetic nature and due to desorption of hydration water; for larger hydration it is entropic and suggested to involve water depolarization. This antagonistic nature and the presence of various compensating contributions indicate that the hydration repulsion is less universal than previously assumed and rather involves finely tunedsurface-water interactions. doi

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