Peptides, pH, and electrophoresis

Question

I'm trying to determine if there's any truth to a claim that the pH of a buffer does't matter, because a polypeptide composed of a string of alanine residues won't move in the electrophoresis, because an alanine side chain is always uncharged.

 

 

I've sketched a short polypeptide chain of alanine's connected with peptide bonds, however, i'm not quite sure how to determine if there are ionizable groups and how to determine what charges/pH's are to be expected from a peptide chain composed of only alanine 

Answer 1

alanine residues won't move in the electrophoresis, because an alanine side chain is always uncharged.

 

 

by adding SDS which coats the peptides with -ve charge, you can make the peptide move in electrophoresis.

 

if you do not want the peptide to be at physiological pH, the pH of the buffer matters.