Study on Complexation of Proteins with Polyelectrolytes

蛋白质与天然和合成的聚电解质在水溶液体系中的络合作用从两个角度来看是令人感兴趣的。第一个问题是聚合物与非柔性蛋白质分子相互作用的方式，了解这一点可以更好地解释自然界中大分子相互作用的机制。第二个问题涉及在何种程度上保持所得到的复合物的生化活性，这是核心的复合蛋白质聚合物系统，如固定化酶的分子设计，以及使用水溶性polymers.The本研究的蛋白质分离过程的设计已处理与形成蛋白质-聚合物复合物（PPC）在不同的pH值和盐浓度的条件下。采用浊度滴定法、准弹性光散射法、静态光散射法、电泳光散射法和荧光光谱法。我 ...更多信息 此外，在适当的情况下，还采用了生物化学方法，例如测量酶活性。从这些研究中得出的主要结论可以概括如下：（i）PPC主要通过静电力形成;（ii）至少在无盐体系中，蛋白质分子通过1：1化学计量形成离子对与柔性聚电解质复合（或盐键）;（iii）蛋白质分子和蛋白质分子之间的离子对非常弱，其中一些结合被pH值的变化以及小离子和聚离子的加入所切断;（iv）复合物中保留了一定的生物化学功能，因此，复合作用不会引起蛋白质分子三维构象的变化而导致原有功能的丧失，从上述结果可以推断PPC的形成过程如下：首先，许多蛋白质分子与一个聚离子结合形成聚合物内复合物;特别是在无盐体系中，其所有的聚离子电荷被蛋白质的相反电荷化学计量地中和。在此之后，所得的聚合物内复合物彼此相互作用，产生聚集体或凝聚体。这种聚合物内PPC很可能是由许多蛋白质分子通过一个延伸的桥连或捆绑在一起组成的。保持聚合物内PPC结构的盐键似乎非常松散，因为pH值的变化或其他聚离子的加入切断了一些盐键。这种松散性可以使蛋白质和聚离子分子通过热运动与带相反电荷的基团进行化学计量中和。少

The complexation of proteins with natural and synthetic polyelectrolytes in an aqueous system in interesting from two points of view. The first concerns the way in which the polymers interact with non-flexible protein molecules, an understanding of which could provide a better explanation of the mechanisms of macromolecular interaction available in nature. The second concerns the extent to which biochemical activity is maintained in the resulting complexes, the answer to which is central to the molecular design of composite protein-polymer systems, such as immobilized enzymes, as well as the design of protein separation processes using water-soluble polymers.The present study has dealt with the formation of protein-polyelectrolyte complexes (PPCs) under different conditions of pH and salt concentration. Turbidimetric titration, quasi-elastic light scattering (QELS), static light scattering (SLS), electrophoretic light scattering (ELS) and fluorescence spectroscopy have been employed. I … More n addition, biochemical methods such as the measurement of enzymatic activity have also been employed in the appropriate cases. The main conclusions derived from these previous studies may be summarized as follows : (i) PPCs are formed mainly through electrostatic forces ; (ii) in salt-free systems, at least, protein molecules are complexed with flexible polyelectrolytes through 1 : 1 stoichiometric formation of ion pairs (or salt linkages) between oppositely charged groups ; (iii) the ion pairs between the polyelectrolyte and protein molecules are very weak, some of these bindings severed by changes in pH and the addition of small ions and polyions ; and (iv) there is an appreciable retention of biochemical function in theresultant complexes ; therefore, changes in the three-dimensional conformations of the protein molecules caused by complexation are not so large as to cause a loss of original functions.From the above results the processes of PPC formation may be inferred as follows : At first, many protein molecules are bound to one polyion to form an intrapolymer complex ; especially in salt-free systems, all of its polyion charges are stoichiometrically neutralized by the opposite charges of the proteins. After this, the resultant intrapolymer complexes interact with one another, yielding aggregates or coacervates. It appears likely that such an intrapolymer PPC consists of a number of protein molecules bridged or bundled together by one extended polyelectrolyte ion. The salt linkages maintaining the structure of the intrapolymer PPC seem to be very loose, because changes in pH or additions of other polyions sever some of the salt linkages. This looseness may make it possible for the protein and polyion molecules to undergo stoichiometric neutralization with oppositely charged groups through thermal motion. Less