The amount of energy required to split the double strand $DNA$ into two single strands is . . . .kcal $mol ^{-1}$.
[Given: Average energy per $H$-bond for $A - T$ base pair $=1.0 kcal mol ^{-1}, G - C$ base pair $=1.5 kcal mol ^{-1}$, and $A - U$ base pair $=1.25 kcal mol ^{-1}$. Ignore electrostatic repulsion between the phosphate groups.]

| $pH$ at Isoelectric point | |
| $(Amino acid)_I$ | $6$ |
| $(Amino acid)_{II}$ | $9.8$ |
| $(Amino acid)_{III}$ | $3.9$ |
$(Amino acid)_{II}$ is ____ ?