You are trying to purified two versions of protein a.1- the wild-type (nonmutated) protein and 2- a mutant version with a 3 amino acids substitution. you treated both samples the exact way and passed them through ion-exchange column (with positive matrix). you noticed that the mutant protein of a runs through the column more slowly than the wild type. what changes in the mutant protein is most likely to explain this result?

 Dimers formed by a normal protein will run through the gel-filtration column faster than a mutant protein Y monomer. Choice (b) is unlikely, because gel-filtration columns separate proteins on the basis of size, not charge or affinity for small molecules. Choice (c) is unlikely, because if the mutant protein were larger than normal it would be less able to enter the porous beads and would run through the column faster than the normal protein. Choice (d) is unlikely, because a small change in shape without a change in size 
would be unlikely to have a major effect on the behavior of a protein in a gel-filtration column.