Titrate A Peptide and Determine pI
1. View the white board lesson onTitration of Histidine and pI determination
2. Each group will have a different Peptide,
Orange: YIQA
Gold: GWET
Green: SCLF
Blue: VRPN
Purple: MDKI
pKa for the carboxy terminus = 3.0, the amino terminus = 8.0, use the pKR from the book.
For Wednesday, September 24th on two sheets of paper (or less):
- Draw your peptide (all bonds, with every proton on the molecule) and put the pKa values next to each ionizable hydrogen
- Use short hand notation to show each structure of your peptide as each proton is ionized (see the histidine lesson)
- Draw a curve for the titration of 0.12M peptide with 0.2M sodium hydroxide.
- Include all volumes and pH values for
- the beginning, when no base has been added
- each endpoint
- each half way point
- the last endpoint
- the pI
Show the equations that you used to calculate each of the above pH values.