Light Scattering Studies of the Binding of Bovine Serum Albumin to a Cationic Indianapolis , IN 46202 Polyelectrolyte

Pol~v(dimethyldiul1ylammonii~m chloride) (PDMDAAC) exhibits u strong electrmtatic interaction with bovine serum albumin (BSA) at pH 8.0 in 0.16M NaCl. Electrophoretic. dynamic, und static light scuttering suggest that the mode of binding of BSA to PDMDAAC depends upon the weight concentration ratio (r) qf BSA to PDMDAAC. When r is smaller than cu. 10, the system exhibits characteristics ofcooperative binding, in that the BSA molecules are inhomogmw)uslji distributed among the polymer chains, and free PDMDAAC molecules coexist with complex. When r reaches cu. 10. the amount of free PDMDAAC is too small to be observed. Further increase in r leads to a secondary binding process along with an increase in the umoiint qffiee protein. Hydrophobic interactions among the bound BSA are proposed as the driving,fi)rce,fbr the cooperative binding.