Scelta multipla
Calculate the approximate pI of the peptide: C-G-E-K.
366
views
3
rank
1
comments
4. Protein Structure
Isoelectric Point of a Peptide
Scelta multipla
Estimate the isoelectric point of the following dipeptide in the figure.
A
4.75
B
7
C
9.5
D
10.5
Guida verificata passo dopo passo1
Identify the amino acids in the dipeptide. The structure shows a dipeptide composed of cysteine and histidine.
Determine the pKa values for the ionizable groups in the dipeptide. Cysteine has a side chain pKa around 8.3, and histidine has a side chain pKa around 6.0. The amino group has a pKa around 9.0, and the carboxyl group has a pKa around 2.0.
List all the pKa values: pKa1 (carboxyl group) = 2.0, pKa2 (histidine side chain) = 6.0, pKa3 (cysteine side chain) = 8.3, pKa4 (amino group) = 9.0.
To find the isoelectric point (pI), identify the pKa values that correspond to the zwitterionic form of the dipeptide. This is typically between the pKa of the side chain of histidine and the amino group.
Calculate the isoelectric point (pI) by averaging the pKa values that flank the zwitterionic form: pI = (pKa2 + pKa4) / 2.
Video correlati
Pratica correlata
