Jho Y S, Kim M W, Safran S A, Pincus P A
Materials Research Laboratory, University of California at Santa Barbara, 93106, Santa Barbara, CA, USA.
Eur Phys J E Soft Matter. 2010 Feb;31(2):207-14. doi: 10.1140/epje/i2010-10567-5. Epub 2010 Feb 18.
Membranes containing highly charged biomolecules can have a minimal free-energy state at small separations that originates in the strongly correlated electrostatic interactions mediated by counterions. This phenomenon can lead to a condensed, lamellar phase of charged membranes that coexists in thermodynamic equilibrium with a very dilute membrane phase. Although the dilute phase is mostly water, entropy dictates that this phase must contain some membranes and counterions. Thus, electrostatics alone can give rise to the coexistence of a condensed and an unbound lamellar phase. We use numerical simulations to predict the nature of this coexistence when the charge density of the membrane is large, for the case of multivalent counterions and for a membrane charge that is characteristic of biomolecules. We also investigate the effects of counterion size and salt on the two coexisting phases. With increasing salt concentration, we predict that electrostatic screening by salt can destroy the phase separation.
含有高电荷生物分子的膜在小间距时可具有最小自由能状态，这源于由抗衡离子介导的强相关静电相互作用。这种现象可导致带电膜的凝聚层状相，该相在热力学平衡中与非常稀薄的膜相共存。尽管稀薄相主要是水，但熵决定该相必须包含一些膜和抗衡离子。因此，仅静电作用就能导致凝聚层状相和未结合层状相的共存。我们使用数值模拟来预测当膜的电荷密度很大时、对于多价抗衡离子的情况以及对于具有生物分子特征的膜电荷时这种共存的性质。我们还研究了抗衡离子大小和盐对两个共存相的影响。随着盐浓度的增加，我们预测盐的静电屏蔽会破坏相分离。
