Continuous Multicomponent Focusing of Solutes and Particles Using Spatially Stabilized pH

本研究建议使用磁稳定流化床（MSFB）通过不同的等电值（即分子不带电的pH值）来分离两性离子分子（即含有负电荷和正电荷的分子）。流化床由一管组成，带负电荷的树脂颗粒从管的顶部加入，流化液从管的底部分布。从底部去除颗粒，从顶部去除液体，允许连续操作。通过插入高pH值的液体进料和低pH值的固体颗粒来维持床层的pH梯度。含有溶解溶质（其中一种是分离的目标）的混合物被送入靠近底部的液体流中，并进入柱的一侧。当溶质通过液体运动向上移动时，溶质所处的局部pH值降低。局部pH值的降低导致溶质最终带正电（在床层中刚好高于局部pH值等于溶质等电值的位置）。一旦带正电，溶质就会静电地与带负电的树脂结合，并随树脂颗粒一起被带到柱的底部。当溶质沿柱下降时，局部pH值降低，这导致溶质逆转其电荷，从树脂颗粒中移除，并被向上流动的液体所带走。这样，溶质就被困在柱中一个狭窄的区域，在这个区域内，局部pH值等于溶质的等电点。理想情况下，混合物中的溶质会分离到柱中不同层次的区域。通过从这些区域中抽取流体和固体，可以得到富含一种溶质的液体，从而实现分离。拟议的研究将开发一个工作原型，并确定床的有效性，以制备分离的生物分子。

This study proposes using a magnetically stabilized fluidized bed (MSFB) to separate zwitterionic molecules (i.e., molecules containing negatively and positively charged moieties) by virtue of differing isoelectric values (i.e., the pH at which the molecule is not charged). The fluidized bed consists of a tube in which negatively charged resin particles are added from the top of the tube, and the fluidizing liquid is distributed from the bottom. Removal of the particles from the bottom, and liquid from the top allows for continuous operation. A pH gradient is maintained in the bed by inserting the liquid feed at a high pH and the solid particles at a low pH. A mixture containing dissolved solutes (one of which is targeted for separation) is fed into the liquid stream somewhere near the bottom, and to one side of the column. As the solute moves up the bed by virtue of the liquid motion, the local pH that the solute is exposed to decreases. The reduction in the local pH causes the solutes to eventually become positively charged (at the positions in the bed just above the positions where the local pH is equal to the isoelectric values of the solutes). Once positively charged, the solute binds electrostatically to the negatively charged resin, and is carried with the resin particles down to the bottom of the column. As it descends down the column, the local pH decreases, and this causes the solute to reverse its charge, remove itself from the resin particle, and become entrained in the upflowing liquid. The solute thus becomes trapped in a narrow zone at a level in the column where the local pH is equal to the solute's isoelectric point. Ideally, the solutes in the mixture will separate out into zones occupying different levels in the column. By withdrawing fluid and solid from these zones, liquid rich in one solute can be obtained, thereby effecting the separation. The proposed research will develop a working prototype, and scope the effectiveness of the bed to prepare separations of biological molecules.