Grosse Constantino, Zimmerman Viviana
Departamento de Física, Universidad Nacional de Tucuman, Av. Independencia 1800, (4000) S.M. de Tucuman, Argentina.
J Phys Chem B. 2005 Sep 29;109(38):18088-95. doi: 10.1021/jp053074b.
The dielectric and electrokinetic properties of aqueous suspensions of vesicles (unilamellar liposomes) are numerically calculated in the 1 Hz to 1 GHz frequency range using a network simulation method. The model consists of a conducting internal medium surrounded by an insulating membrane with fixed surface charges on both sides. Without an applied field, the internal medium is in electric equilibrium with the external one, so that it also bears a net volume charge. Therefore, in the presence of an applied ac field, there is fluid flow both in the internal and in the external media. The obtained results are qualitatively different from those corresponding to suspensions of charged homogeneous particles, mainly due to the existence of an additional length scale (the membrane thickness) and the corresponding dispersion mechanism, charging of the membrane. Because of this dispersion, the shapes of the spectra change with the size of the particles (at constant zeta potential and particle radius to Debye length ratio) instead of merely shifting along the frequency axis. A comparison between the numerical results and those obtained using approximate analytical expressions shows deviations that are, in general, sufficiently large enough to show the necessity to use numerical results in order to interpret broad frequency range dielectric and electrokinetic measurements of vesicle suspensions.
使用网络模拟方法，在1赫兹至1吉赫兹频率范围内对囊泡（单层脂质体）水悬浮液的介电和电动特性进行了数值计算。该模型由一个导电内部介质组成，其周围是一个绝缘膜，两侧带有固定表面电荷。在没有外加电场的情况下，内部介质与外部介质处于电平衡状态，因此它也带有净体电荷。因此，在存在外加交流电场的情况下，内部和外部介质中都会有流体流动。所得结果在性质上与带电均匀颗粒悬浮液的结果不同，主要是由于存在额外的长度尺度（膜厚度）和相应的色散机制，即膜的充电。由于这种色散，光谱的形状会随着颗粒大小而变化（在恒定的zeta电位和颗粒半径与德拜长度比的情况下），而不是仅仅沿频率轴移动。数值结果与使用近似解析表达式获得的结果之间的比较表明，一般来说，偏差足够大，足以表明为了解释囊泡悬浮液的宽频介电和电动测量结果，有必要使用数值结果。
