Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
University of Goettingen, Institute for Microbiology and Genetics, 37077 Göttingen, Germany.
Phys Rev Lett. 2018 Mar 23;120(12):128103. doi: 10.1103/PhysRevLett.120.128103.
The formation and closure of aqueous pores in lipid bilayers is a key step in various biophysical processes. Large pores are well described by classical nucleation theory, but the free-energy landscape of small, biologically relevant pores has remained largely unexplored. The existence of small and metastable "prepores" was hypothesized decades ago from electroporation experiments, but resolving metastable prepores from theoretical models remained challenging. Using two complementary methods-atomistic simulations and self-consistent field theory of a minimal lipid model-we determine the parameters for which metastable prepores occur in lipid membranes. Both methods consistently suggest that pore metastability depends on the relative volume ratio between the lipid head group and lipid tails: lipids with a larger head-group volume fraction (or shorter saturated tails) form metastable prepores, whereas lipids with a smaller head-group volume fraction (or longer unsaturated tails) form unstable prepores.
水孔在双层脂膜中的形成和闭合是各种生物物理过程的关键步骤。大孔很好地用经典成核理论来描述，但小的、与生物学相关的孔的自由能景观在很大程度上仍未被探索。几十年前，从电穿孔实验中假设了小的、亚稳态的“前孔”的存在，但从理论模型中解析亚稳态前孔仍然具有挑战性。使用两种互补的方法——原子模拟和最小脂质模型的自洽场理论——我们确定了在脂质膜中出现亚稳态前孔的参数。这两种方法都一致表明，孔的亚稳性取决于脂质头部基团和脂质尾部之间的相对体积比：具有较大头部基团体积分数（或较短的饱和尾部）的脂质形成亚稳态前孔，而具有较小头部基团体积分数（或较长的不饱和尾部）的脂质形成不稳定的前孔。
