reaction. To the contrary, the complexations between linear
The electrophoretic light scattering method was applied to meapolyelectrolytes and proteins have been widely studied in sure the electrophoretic mobility of the complex formed between the fields of protein recovery (7-13) and colloid titration lysozyme and sodium dextran sulfate with an average molecular (14, 15) by use of the precipitation technique. Recently, weight of 5.0 1 10 5 . The electrophoretic mobility of the complex the complex formation mechanism has been investigated by was examined as a function of the lysozyme concentration added application of dynamic and electrophoretic light scattering to 1.0 mM sodium dextran sulfate suspension containing 2.8 mM methods to the polyelectrolyte solutions .
sulfate group. The mobility of the dextran sulfate was 03.5 1
The purpose of the present study is to examine the electro-10 08 m 2 s 01 V 01 in the absence of lysozyme. The magnitude of phoretic mobilities of the complexes between lysozyme and the negative mobility decreased abruptly below a molar lysozyme/ sodium dextran sulfate ratio ( R) of 1.0. The electrophoretic mobil-sodium dextran sulfates with average molecular weights of ity again changed in the R range from 100 to 300, and the sign 5.0 1 10 5 and 2.5 1 10 4 by the electrophoretic light scatterof the mobility changed from negative to positive at R Å 220. To ing method. A possible interaction mechanism of the dextran the contrary, when lysozyme was bound to sodium dextran sulfate, sulfates with a protein is proposed on the basis of not only the sodium ions were released from this polyelectrolyte. The numthe mobilities of the complexes but also the binding quantity ber of ions released was determined from the ratio of the increment of protein and the number of sodium ions released from the of free sodium ion concentration to the binding amount of the polymer chain upon the binding.
protein to be 4.6 { 0.2 per bound lysozyme. The complex of lysozyme with dextran sulfate with a molecular weight of 2.5 1 10 4 MATERIALS AND METHODS was also examined. The same dependence of the electrophoretic mobility on the added lysozyme concentration was obtained as Sodium dextran sulfates with average molecular weights that in the case of the dextran sulfate with a molecular weight of of 5.0 1 10 5 (DEX500) and 2.5 1 10 4 (DEX25) were 5.0 1 10 5 , for polyelectrolyte suspensions prepared with the same sulfate group concentration.