Phenylalanine has two known pKa charges: 1.83 and 9.13. To determine their individual ionic dissociation charges at pH 10, the equation to be used is
pH = pKa + log [α/(1-α)]
At pKa 1.83:
10 = 1.83 + log [α₁/(1-α₁)]
α₁ = 0.99999
At pKa 9.13:
10 = 9.13 + log [α₂/(1-α₂)]
α₂ = 0.88114
Average Net Charge = 0.99999 + 0.88114 = 1.88
