Would like to have your comment how the "electric charge" of
cytochrome C can help in purifying this protein. What does this
electric charge have to do in helping to purify this protein. I know
it is a physical property, but please comment on how it helps in this
purification of cytochrome C. Among many other proteins in the "mix",
how does the "electric charge" identifies Cytochrome C against all the
others.

                                    Ted.

Most proteins carry a negative charge at neutral pH. Cytochrome C
differs in that it carries a positive charge. This aids in separation
from other proteins through ion exchange chromatography, wherein in
this particular case a column packed with a media carrying a negative
charge is used to hold Cytochrome C until is it eluted with a
concentrated salt solution.

Here is a link to an protocol that details purification of cytochrome
C from bovine heart muscle utilizing various separation techniques.
These procedures could easily be applied to a protein mixture as well.

http://www.science.smith.edu/departments/Biochem/Biochem_353/cytoprep.html