Electrophoretic Light Scattering Study of Sodium Dextran Sulfate-Lysozyme Complex

Author： Yamaguchi K. Hachiya K. Moriyama Y. Takeda K.

ISSN： 0021-9797

Source： Journal of Colloid and Interface Science, Vol.179, Iss.1, 1996-04, pp. : 249-254

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Abstract

The electrophoretic light scattering method was applied to measure the electrophoretic mobility of the complex formed between lysozyme and sodium dextran sulfate with an average molecular weight of 5.0 x 10 5 . The electrophoretic mobility of the complex was examined as a function of the lysozyme concentration added to 1.0 mu M sodium dextran sulfate suspension containing 2.8 m M sulfate group. The mobility of the dextran sulfate was -3.5 x 10 -8 m 2 s -1 V -1 in the absence of lysozyme. The magnitude of the negative mobility decreased abruptly below a molar lysozyme/sodium dextran sulfate ratio ( R ) of 1.0. The electrophoretic mobility again changed in the R range from 100 to 300, and the sign of the mobility changed from negative to positive at R = 220. To the contrary, when lysozyme was bound to sodium dextran sulfate, the sodium ions were released from this polyelectrolyte. The number of ions released was determined from the ratio of the increment of free sodium ion concentration to the binding amount of the protein to be 4.6 ± 0.2 per bound lysozyme. The complex of lysozyme with dextran sulfate with a molecular weight of 2.5 x 10 4 was also examined. The same dependence of the electrophoretic mobility on the added lysozyme concentration was obtained as that in the case of the dextran sulfate with a molecular weight of 5.0 x 10 5 , for polyelectrolyte suspensions prepared with the same sulfate group concentration.