The substituents R1 and R2 for nine peptides are listed in the table given below. How many of these peptides are positively charged at pH = 7.0?

Four peptides (IV, VI, VIII and IX) are positively charged at pH 7.0. These peptides have isoelectric point (pI) more than 7. In the neutral solution (pH=7), they exist as cations. Hence, the given peptide is of basic nature. Hence, it must contain two or more amino groups.