About amino acid in different pH~?

  • Thread starter Thread starter Weeze R
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Weeze R

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When one amino acid is put in different pH, I know how to draw its structure(refers to which group is doing protonation or deprotonation) by comparing its pKa value with the pH. But when I have a peptide. Do I consider each a.a individually(like, do the protonation or deprotonation of each a.a before they are forming peptide bond) OR do the protonation or deprotonation as a whole group (like, after each a.a has connected together and then do the protonation or deprotonation )

Srry about the wording... But reeally need help on this
THX!!!!
 
You would consider the protonation/deprotonation of the entire peptide chain. You will need to take into consideration the protons on the N terminus and C terminus of the peptide chain as well as any donating or acepting protons on the R groups of individual amino acids. For problems like this it may be best to draw a titration curve as well as the structure of the peptide chain fully protonated (noting the pH of when the proton on each R group is protonated). Hope this helps!
 
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