A comparative dielectric study of human serum low density lipoprotein before and after partial digestion by trypsin.

The relative permittivity of aqueous solutions of human serum low density lipoprotein (LDL) and partially trypsin digested lipoprotein (T-LDL) has been determined for various concentrations at 20 degrees C over the frequency range 0.15-100 MHz. Comparison of the dielectric dispersion curves for the digested lipoprotein with those for the native preparation revealed a larger low-frequency dielectric increment, which may be attributed to an increase in the number of counterions moving over the surface of the molecule. An explanation of this observation is an elevation of 70% in the net negative charge on the surface of the trypsin-treated particle as compared to its native counterpart.