Native Gel Electrophoresis

Practice: Which advantage does native gel electrophoresis provide as a protein technique?

Practice: Which option below best describes the native gel electrophoresis migration for Proteins A, B, C & D (assuming equal mass & shape) considering that the buffer solution has a pH = 6.4. 

Protein A pI = 5.2, Protein B pI = 6.4, Protein C pI = 7.0, Protein D pI = 9.2

Practice: A) Consider both the peptide Gly—Pro—Ser—Glu—Thr (in a linear chain) and a cyclic peptide of the same exact sequence Gly—Pro—Ser—Glu—Thr (with a peptide bond linking the Thr & Gly). Are these peptides chemically the same? Explain.

B) Can you expect to separate the peptides above by Native-PAGE? Why or why not?