In: Chemistry
What is the pI for Lys-Glu-Ser?
Lys-Glu-Ser peptide is which can be represented as
,simply
Now, the cationic and/or anionic forms of Lys-Glu-Ser upon pH
changing are given as
Hence, from the above pH values we can determine the
pKa s of the corresponding functional groups as
followsFrom the definition of the
isoelectric point we know that
where, pK1 and pK2 are the pKa
values of the monocation and monoanion form and from the above pH
diagram it is clear that if we consider the overall neutral form
which is created via step-B from monocation and destroyed via
step-C to monoanion. So, the two pKa s that we are
looking for are the pKa of the terminal NH2
ie. 8.5 and the the pKa of the branched COOH ie. 3.5. So, from the
formula we can calculate the Pi of the peptide