Peptide ionization Consider a peptide with the sequence Ser-His-Glu-Cys-Arg-Gln. You will be asked to state the charge on the functional groups of this peptide at pH 1 and pH 9.5. You will also be asked to calculate the net charge on the peptide. You may find it convenient to write down the charge on each group on a piece of paper as you go along, so that you can add them up at the end.
Peptide ionization Consider a peptide with the sequence Ser-His-Glu-Cys-Arg-Gln. You will be asked to state the charge on the functional groups of this peptide at pH 1 and pH 9.5. You will also be asked to calculate the net charge on the peptide. You may find it convenient to write down the charge on each group on a piece of paper as you go along, so that you can add them up at the end.
Biochemistry
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ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Can you please help find the net charge?
Transcribed Image Text:Peptide lonization
Consider a peptide with the sequence Ser-His-Glu-Cys-Arg-Gln.
You will be asked to state the charge on the functional groups of this
peptide at pH 1 and pH 9.5.
You will also be asked to calculate the net charge on the peptide. You may
find it convenient to write down the charge on each group on a piece of
paper as you go along, so that you can add them up at the end.
Assume the following generic pK, values for ionizable functional groups:
a-carboxyl:
side-chain carboxyl:
imidazole:
3.1
4.1
6.0
a-amino:
8.0
thiol:
8.3
E-amino:
10.8
aromatic hydroxyl:
guanidino:
10.9
12.5
Transcribed Image Text:The net charge on this peptide at pH 1 is
1
+2
+3
+1
-3
-2
O O OO O O
Expert Solution
Step 1
The net charge of the each amino acid residue in a peptide is determined by the side chain pK of the amino acid, along with the alpha amino and alpha carboxyl group at the N- and C-terminal ends respectively. It is also determined by the pH of the buffer in which the peptide is dissolved.
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