Shim Jaesool, Dutta Prashanta, Ivory Cornelius F
School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920, USA.
J Nanosci Nanotechnol. 2008 Jul;8(7):3719-28.
Numerical simulations are presented for ampholyte-based isoelectric focusing in 2D microgeometries. In this study, model proteins are focused in the presence of 25 biprotic ampholytes under an applied electric field. Each protein is considered as a simple polypeptide having ten charge states, while the biprotic ampholytes are selected to generate a shallow pH range of 6 to 9. Straight and contraction-expansion microchannels are considered here, and a nominal electric field of 300 V/cm is maintained for separation of proteins. Six distinct values of deltapKs between 1 and 3.5 are investigated for ampholytes to form pH profiles in a 1 cm long microchannel. Simulation results show that relatively larger values of deltapK(deltapK > 3) are required to form stepless pH profiles in the system. The peak heights and differential resolutions of focused proteins are much higher for lower values of deltapK for which a stepped pH profile is evident. For each protein, the time it takes for the two edges of a peak to merge increases linearly with deltapK, while the focusing time goes up exponentially with increasing deltapK. Both merging and focusing times of protein are higher for contraction-expansion microchannel than those of straight microchannel. For a particular value of deltapK, the contracted "Zoom" region of contraction-expansion channel is able to form more tightly focused bands than the expanded region.
本文给出了基于两性电解质的二维微几何等电聚焦的数值模拟。在本研究中，模型蛋白在施加电场的情况下，于25种两性电解质存在时实现聚焦。每种蛋白被视为具有十种电荷状态的简单多肽，而所选的两性电解质可产生6至9的浅pH范围。这里考虑了直微通道和收缩 - 扩张微通道，为分离蛋白维持300 V/cm的标称电场。研究了两性电解质在1至3.5之间的六个不同的ΔpK值，以在1 cm长的微通道中形成pH分布。模拟结果表明，需要相对较大的ΔpK值（ΔpK > 3）才能在系统中形成无阶跃的pH分布。对于较低的ΔpK值，聚焦蛋白的峰高和分辨率差异更高，此时明显呈现阶跃式pH分布。对于每种蛋白，峰的两个边缘合并所需的时间随ΔpK线性增加，而聚焦时间随ΔpK增加呈指数上升。收缩 - 扩张微通道中蛋白的合并时间和聚焦时间均高于直微通道。对于特定的ΔpK值，收缩 - 扩张通道的收缩“缩放”区域能够比扩张区域形成更紧密聚焦的条带。
