Amino acids and peptides The “Lego” of proteins www.freelivedoctor.com
Amino Acids <ul><li>Same general structure </li></ul><ul><li>Called alpha amino acids </li></ul><ul><li>L- isomer is physi...
Amino Acids, General <ul><li>pK of carboxyl group around 2.3 </li></ul><ul><ul><li>Deprotonated at physiological pH </li><...
Nonpolar amino acids www.freelivedoctor.com
Aromatic Amino Acids www.freelivedoctor.com
Polar Amino Acids, alcohols www.freelivedoctor.com
Polar Amino Acids (sulfur containing) www.freelivedoctor.com
Polar amino acids (amides) www.freelivedoctor.com
Charged Amino Acids (Acidic) www.freelivedoctor.com
Charged Amino Acids (Basic) www.freelivedoctor.com
Titration of Amino acids <ul><li>Titration of glycine </li></ul>www.freelivedoctor.com
Titration of Glutamate www.freelivedoctor.com
Purification of amino acids <ul><li>Chromatography </li></ul><ul><ul><li>Various types </li></ul></ul><ul><ul><li>Ion exch...
Electrophoresis <ul><li>Using electricity to move particles through a gelatinous matrix </li></ul><ul><li>Isoelectric poin...
Peptides <ul><li>Peptide bond is amide linkage between amino acids </li></ul><ul><li>No free rotation about C-N bond due t...
Tetrapeptide <ul><li>Note planes of peptide bonds </li></ul>www.freelivedoctor.com
Peptides <ul><li>Peptides are vectorial </li></ul><ul><ul><li>Have N and C termini </li></ul></ul><ul><li>Sequences read H...
Draw a tetrapeptide of L-A-R-D at physiological pH <ul><li>Answer </li></ul>www.freelivedoctor.com
Biologically Interesting Peptides <ul><li>Aspartame </li></ul><ul><ul><li>L-aspartyl-Lphenylalanine methyl ester </li></ul...
Other small interesting peptides <ul><li>Enkephalins </li></ul><ul><li>  Y-G-G-F-L </li></ul><ul><ul><li>Y-G-G-F-M </li></...
Chemical Synthesis of Peptides <ul><li>Why? </li></ul><ul><li>Done solid phase </li></ul><ul><ul><li>Problem with in solut...
Scheme for peptide synthesis www.freelivedoctor.com
Tetrapeptide answer www.freelivedoctor.com
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Cell Anatomy

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Cell Anatomy

  1. 1. Amino acids and peptides The “Lego” of proteins www.freelivedoctor.com
  2. 2. Amino Acids <ul><li>Same general structure </li></ul><ul><li>Called alpha amino acids </li></ul><ul><li>L- isomer is physiologically active </li></ul><ul><li>Side chain or R group determines other properties </li></ul><ul><li>Acid-base properties </li></ul>www.freelivedoctor.com
  3. 3. Amino Acids, General <ul><li>pK of carboxyl group around 2.3 </li></ul><ul><ul><li>Deprotonated at physiological pH </li></ul></ul><ul><ul><ul><li>R – COO - </li></ul></ul></ul><ul><li>pK of amino group around 9.5 </li></ul><ul><ul><li>Protonated at physiological pH </li></ul></ul><ul><ul><ul><li>H 3 N + -R </li></ul></ul></ul><ul><li>Some R-groups are acidic or basic </li></ul>www.freelivedoctor.com
  4. 4. Nonpolar amino acids www.freelivedoctor.com
  5. 5. Aromatic Amino Acids www.freelivedoctor.com
  6. 6. Polar Amino Acids, alcohols www.freelivedoctor.com
  7. 7. Polar Amino Acids (sulfur containing) www.freelivedoctor.com
  8. 8. Polar amino acids (amides) www.freelivedoctor.com
  9. 9. Charged Amino Acids (Acidic) www.freelivedoctor.com
  10. 10. Charged Amino Acids (Basic) www.freelivedoctor.com
  11. 11. Titration of Amino acids <ul><li>Titration of glycine </li></ul>www.freelivedoctor.com
  12. 12. Titration of Glutamate www.freelivedoctor.com
  13. 13. Purification of amino acids <ul><li>Chromatography </li></ul><ul><ul><li>Various types </li></ul></ul><ul><ul><li>Ion exchange </li></ul></ul><ul><ul><ul><li>Uses net charge or can change with pH </li></ul></ul></ul><ul><ul><ul><ul><li>Separate K, D and A </li></ul></ul></ul></ul><ul><ul><li>HPLC </li></ul></ul>www.freelivedoctor.com
  14. 14. Electrophoresis <ul><li>Using electricity to move particles through a gelatinous matrix </li></ul><ul><li>Isoelectric point </li></ul><ul><li>IEF </li></ul>www.freelivedoctor.com
  15. 15. Peptides <ul><li>Peptide bond is amide linkage between amino acids </li></ul><ul><li>No free rotation about C-N bond due to partial double bond character of bond </li></ul><ul><ul><li>resonance </li></ul></ul>www.freelivedoctor.com
  16. 16. Tetrapeptide <ul><li>Note planes of peptide bonds </li></ul>www.freelivedoctor.com
  17. 17. Peptides <ul><li>Peptides are vectorial </li></ul><ul><ul><li>Have N and C termini </li></ul></ul><ul><li>Sequences read H 3 N + ---COO - </li></ul><ul><ul><li>P-I-G </li></ul></ul>www.freelivedoctor.com
  18. 18. Draw a tetrapeptide of L-A-R-D at physiological pH <ul><li>Answer </li></ul>www.freelivedoctor.com
  19. 19. Biologically Interesting Peptides <ul><li>Aspartame </li></ul><ul><ul><li>L-aspartyl-Lphenylalanine methyl ester </li></ul></ul>www.freelivedoctor.com
  20. 20. Other small interesting peptides <ul><li>Enkephalins </li></ul><ul><li> Y-G-G-F-L </li></ul><ul><ul><li>Y-G-G-F-M </li></ul></ul><ul><li>Oxytocin </li></ul><ul><ul><li>C-Y-I-Q-N-C-P-L-G-NH 2 </li></ul></ul><ul><ul><ul><li>Has C—C disulfide </li></ul></ul></ul><ul><li>Vasopressin </li></ul><ul><ul><li>C-Y-F-Q-N-C-P-R-G-NH 2 </li></ul></ul><ul><ul><ul><li>Also disulfide </li></ul></ul></ul>www.freelivedoctor.com
  21. 21. Chemical Synthesis of Peptides <ul><li>Why? </li></ul><ul><li>Done solid phase </li></ul><ul><ul><li>Problem with in solution </li></ul></ul><ul><ul><ul><li>Hard to make pure desired sequence </li></ul></ul></ul><ul><ul><li>Purify by filtration </li></ul></ul><ul><li>Side chains blocked </li></ul><ul><li>Made backwards ( C---N) </li></ul>www.freelivedoctor.com
  22. 22. Scheme for peptide synthesis www.freelivedoctor.com
  23. 23. Tetrapeptide answer www.freelivedoctor.com
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