Johansson H O, Lundh G, Karlström G, Tjerneld F
Department of Biochemistry, Lund University, Sweden.
Biochim Biophys Acta. 1996 Aug 13;1290(3):289-98. doi: 10.1016/0304-4165(96)00031-1.
Aqueous two-phase systems composed of ethylene oxide/propylene oxide random co-polymers, EO30/PO70 or Ucon (EO50/PO50), in the top phase and dextran T500 in the bottom phase, have been studied. The cloud point diagram for EO30/PO70 in water solution was determined. EO30/PO70 has a cloud point of 32 degrees C at a concentration of 10% (w/w). The phase diagram for the system EO30/PO70-dextran T500-water was determined. Salt effects have been studied on the partitioning of two model proteins, bovine serum albumin and hen egg white lysozyme, in EO30/PO70-dextran and Ucon-dextran systems. Ions with different hydrophobicity, i.e., with different position in the Hofmeister or lyotropic series, were investigated with reference to their effect on protein partition. The counterion hydrophobicity was shown to have a strong influence on the partitioning of BSA and lysozyme. Most extreme partitioning was obtained with hydrophobic (chaotropic) ions like CIO4- and I-. A comparison of protein partitioning between PEG-dextran and EO30/PO70-dextran has been done. A more extreme protein partitioning was obtained in the EO30/PO70-dextran containing system. Temperature-induced phase separation was studied with EO30/PO70 at 45 degrees C. Both BSA and lysozyme were completely partitioned to the water phase formed above the cloud point of EO30/PO70. Model calculations, based on Flory-Huggins theory of polymer solutions, have been done which could reproduce the salt effect on the protein partitioning in aqueous-two phase system.
研究了由环氧乙烷/环氧丙烷无规共聚物EO30/PO70或Ucon（EO50/PO50）组成的上相和葡聚糖T500组成的下相的双水相系统。测定了EO30/PO70在水溶液中的浊点图。EO30/PO70在浓度为10%（w/w）时的浊点为32℃。测定了EO30/PO70-葡聚糖T500-水系统的相图。研究了盐对两种模型蛋白牛血清白蛋白和鸡蛋清溶菌酶在EO30/PO70-葡聚糖和Ucon-葡聚糖系统中分配的影响。研究了具有不同疏水性（即在霍夫迈斯特或离液序列中具有不同位置）的离子对蛋白质分配的影响。结果表明，抗衡离子疏水性对牛血清白蛋白和溶菌酶的分配有很大影响。用CIO4-和I-等疏水（促溶）离子获得了最极端的分配。比较了聚乙二醇-葡聚糖和EO30/PO70-葡聚糖之间的蛋白质分配。在含EO30/PO70-葡聚糖的系统中获得了更极端的蛋白质分配。在45℃下用EO30/PO70研究了温度诱导的相分离。牛血清白蛋白和溶菌酶都完全分配到了在EO30/PO70浊点以上形成的水相中。基于聚合物溶液的弗洛里-哈金斯理论进行了模型计算，该计算可以重现盐对双水相系统中蛋白质分配的影响。
