Isoelectric point (pI): The hydrogen ion concentration at which a particular amino acid does not influence by electric field is known as Iso-electric point (pI).
At isoelectric points:
(1) [cation] = [Anion]
(2) Net charge on particular amino acid is zero.
(3) Maximum concentration of zwiter ion
(1) Isoelectric point (pI) of neutral amino acid (for example alanine) is the average of pKa1 and pKa2. For example pI of alanine calculated as:
PI= 1/2(pKa1+pKa2)
(2) Isoelectric point (pI) of acidic amino acid is the average of pKa values of two -COOH groups (uncharged) in its acidic form. For example pI of Glutamic acid calculated as:
(3)Isoelectric point (pI) of basic amino acid is the average of pKa values of two positively charged amine groups in its acidic form. For example pI of lysine calculated as:
Notes: Acidic amino acid has lowest pI value while basic amino acid had highest isoelectric point (pI).
Related topic:
No comments:
Post a Comment