Distortion of the electrophoretic titration curves of some proteins.

The electrophoretic titration curves of complex mixtures of vitamin K-dependent human blood proteins and proteins of Bothrops asper venom were investigated. In both protein mixtures some curves exhibited marked distortions such as additional maxima and minima when Pharmalyte 3-10 carrier ampholytes were used for isoelectric focusing in agarose gels. The distortions result from an unspecific interactions between some carrier ampholyte constituents with particular proteins. The interacting carrier ampholyte components could be completely removed by binding to albumin and ultrafiltration through a UM-2 Amicon membrane with resultant regular titration curves. The interacting carrier ampholyte species were only partially removed by ultrafiltration through a UM-2 membrane without incubation with albumin.