Indicate the net charge of arginine at the chosen pH 9.5.
H2N HN H2N COO
Answered Essay: Indicate the net charge of arginine at the chosen pH 9.5.
Expert Answer
Answer
If pH < pKa, H+ is on. It means that the group is protonated
If it happens to be for -NH2 group, it will have +1 charge.
For -COOH group in this case, there will be no charge
If pH > pKa, H+ is off. It means that the group is de protonated
If it happens to be for -COOH group, it will have -1 charge.
For -NH2 group in this case, there will be no charge
For Arginine:
pKa of acidic part, pKa1 = 2.17
pKa of basic part, pKa2 = 9.04
pKa of side chain, pKa3 = 12.48
It has basic side chain
pH is greater than pKa1. So, acidic part will not have its H+ on
So, negative charge is present because of it
pH is greater than pKa2. So, baisc part will not have H+ on it
So, no charge because of it
pH is less than pKa3 and since it is basic, it will have H+ on it
So, positive charge is present because of it
Hence net charge at pH = 9.5 is 0
