Both 3 and 4 with explanation. thanks.

3. A mutation that causes a substitution from leucine to another amino acid alters the mobility of a protein in native gel electrophoresis at neutral pH as shown here. Which substitution would most likely cause this change? - a. Levcino to serine - b. Loucine to aranine - c. Leucino to truntonhan - d. Leucin to slutamate - elencineto isoleusina 4. What is the net charge (approximately) on the polypeptide shown below at pH 12.5? Lys - Arg - Val - Cys - Glu