Biochemistry question. Please explain your answer

CH3 , Hc H HUN COOH valine HEN histidine H2N COOH phenylalanine B) An aqueous solution (pH ~7) containing mixture of three amino acids; glycine (G), arginine (R) and glutamic acid (E), was dropped onto center of a solid matrix (e.g chromatographic paper) which is incorporated in an electrical circuit (a). After applying electrostatic potential, the aminoacids are separated as shown in b. Determine amino acids that are labeled as 1, 2 and 3