Calculating the theoretical net charge

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SUMMARY

The discussion centers on calculating the theoretical net charge of the amidated peptide GAKKIYPRVSACMIHGGAVIAIDMDGTDA. To determine the net charge, one must analyze the ionizable side groups and their respective pKa values, considering the pH of the solution. The amine terminus remains protonated while the carboxyl terminus is amidated, which influences the overall charge. Participants emphasize the importance of identifying which side groups are protonated or deprotonated at the given pH to accurately assess the net charge.

PREREQUISITES
  • Understanding of peptide structure and terminology
  • Knowledge of pKa values for amino acid side chains
  • Familiarity with the concept of isoelectric point
  • Basic principles of acid-base chemistry
NEXT STEPS
  • Research the pKa values of common amino acid side chains
  • Learn how to calculate the isoelectric point of peptides
  • Study the effects of pH on peptide charge states
  • Explore methods for determining peptide net charge computationally
USEFUL FOR

This discussion is beneficial for biochemists, molecular biologists, and anyone involved in peptide synthesis or analysis, particularly those interested in charge calculations and protein behavior in different pH environments.

researcher87
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I was given this peptide:

GAKKIYPRVSACMIHGGAVIAIDMDGTDA

I then amidated the C-terminal, and i need to figure out how to calculate the theoretical net charge of the amidated peptide.
Can anyone help me please!
I have a feeling it is something to do with the isoelectric point but I'm not sure.
Thanks
 
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Since you have capped the carboxyl terminus (the amine terminus remains), this question is asking you to determine the charges of the side groups of the peptide. Write down all of the peptides that have ionizable side groups and their pKa's. Determine which ones will be protonated and deprotonated at the pH (which is not given by you in your OP). Ignore ion pairs and count the excess negative or excess positive charges. Don't ignore the amine terminus' pKa (as ammonium ion).
 

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