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Cell Anatomy

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Transcript

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

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