Helm C A, Israelachvili J N, McGuiggan P M
Institut für Physikalische Chemie, Johannes Gutenberg-Universität, Mainz, Germany.
Biochemistry. 1992 Feb 18;31(6):1794-805. doi: 10.1021/bi00121a030.
With the aim of gaining more insight into the forces and molecular mechanisms associated with bilayer adhesion and fusion, the surface forces apparatus (SFA) was used for measuring the forces and deformations of interacting supported lipid bilayers. Concerning adhesion, we find that the adhesion between two bilayers can be progressively increased by up to two orders of magnitude if they are stressed to expose more hydrophobic groups. Concerning fusion, we find that the most important force leading to direct fusion is the hydrophobic attraction acting between the (exposed) hydrophobic interiors of bilayers; however, the occurrence of fusion is not simply related to the strength of the attractive interbilayer forces but also to the internal bilayer stresses (intrabilayer forces). For all the bilayer systems studied, a single basic fusion mechanism was found in which the bilayers do not "overcome" their short-range repulsive steric-hydration forces. Instead, local bilayer deformations allow these repulsive forces to be "bypassed" via a mechanism that is like a first-order phase transition, with a sudden instability occurring at some critical surface separation. Some very slow relaxation processes were observed for fluid bilayers in adhesive contact, suggestive of constrained lipid diffusion within the contact zone.
为了更深入地了解与双层粘附和融合相关的力及分子机制，使用表面力仪（SFA）来测量相互作用的支撑脂质双层的力和变形。关于粘附，我们发现，如果对两个双层施加应力以暴露更多疏水基团，它们之间的粘附力可逐步增加高达两个数量级。关于融合，我们发现导致直接融合的最重要的力是双层（暴露）疏水内部之间的疏水吸引力；然而，融合的发生不仅与双层间吸引力的强度有关，还与双层内部应力（层内力）有关。对于所有研究的双层系统，发现了一种单一的基本融合机制，即双层不会“克服”其短程排斥性空间水合力。相反，局部双层变形允许通过一种类似于一级相变的机制“绕过”这些排斥力，在某个临界表面间距处会突然出现不稳定性。对于处于粘附接触的流体双层，观察到了一些非常缓慢的弛豫过程，这表明接触区内脂质扩散受到限制。
