2012年09月01日 訊 /生物谷BIOON/ --生物膜像皮膚那樣包圍著細(xì)胞。它們也包圍著在代謝和細(xì)胞分裂中發(fā)揮著重要功能的細(xì)胞器,?？茖W(xué)家們長期以來在原理上就知道生物膜是如何被構(gòu)建出來的，也知道水分子在維持相鄰的膜之間最佳距離中發(fā)揮著作用,。如今,，在計算機模擬的幫助下，來自德國慕尼黑理工大學(xué)和柏林自由大學(xué)的研究人員發(fā)現(xiàn)兩種不同的機制阻止相鄰的膜表面粘附在一起,。相關(guān)研究結(jié)果刊登在PNAS期刊上。
生物膜鑲嵌有蛋白質(zhì)和脂質(zhì),。這些脂質(zhì)都是雙親媒性分子,，即它們都是由一個親水的極性頭部和一個疏水的非極性尾部組成。由于膜脂的這一結(jié)構(gòu)特點,，它們在水溶液中能自動聚攏形成脂雙分子層,。當(dāng)兩種膜的水溶性表面彼此靠近太近時，水合排斥(hydration repulsion)就產(chǎn)生,，從而阻止膜表面接觸,。在兩個完整的生物膜之間，它們總是存在只有幾納米厚的水薄層,。但是,，在此之前，科學(xué)家們不清楚水合排斥如何在分子水平上發(fā)揮作用,。如今,，研究人員詳細(xì)地闡述了用來解釋水合排斥的這兩種不同機制的重要性,。
在當(dāng)前這項研究中，研究人員發(fā)現(xiàn)根據(jù)生物膜之間的距離,，兩種不同的機制發(fā)揮作用,。如果生物膜之間相隔大約1納米或更大的距離，那么水分子在阻止它們接近時發(fā)揮著決定性的作用,。這時水分子發(fā)揮著類似緩沖器的作用,，將生物膜推開。當(dāng)這種距離相隔更短時,，在相向的生物膜表面上的脂質(zhì)相互抑制它們自己的移動,，從而增加彼此之間的排斥力。(生物谷Bioon.com)
doi: 10.1073/pnas.1205811109
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Hydration repulsion between biomembranes results from an interplay of dehydration and depolarization
Emanuel Schnecka,b,1, Felix Sedlmeiera,b, and Roland R. Netz
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 tuned surface-water interactions.
