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AMINO ACID AND PROTEIN CHEMISTRY

AMINO ACID AND PROTEIN CHEMISTRY. Maria Milagros Untalan-Magat, MD,MEM, FPPS,FPAPP. Protein Structure and Function. OBJECTIVES: General functions of proteins Structural composition of amino acids Chemical properties Hierarchy of protein organization. Objective:. Lifelong learners.

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AMINO ACID AND PROTEIN CHEMISTRY

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  1. AMINO ACID AND PROTEIN CHEMISTRY Maria Milagros Untalan-Magat, MD,MEM, FPPS,FPAPP

  2. Protein Structure and Function OBJECTIVES: • General functions of proteins • Structural composition of amino acids • Chemical properties • Hierarchy of protein organization

  3. Objective: Lifelong learners Independent learners READ YOUR BOOKS!

  4. Proteins • “Proteios” • Polymers of amino acids • 20 amino acids • “Alphabet” of protein structure • Basic structural units

  5. Proteins Diversity in functions • Enzymatic catalysis • Transport and storage • Coordinated motion and mechanical support • Immune protection • Generation and transmission of nerve impulses • Control of growth

  6. COO- COO- NH3+ H H R R NH3+ Amino Acids: Structure Ca Ca L - configuration D - configuration

  7. COO- NH3+ H R Amino Acids: Properties • Tetrahedral carbon • Asymmetric center • Chiral center • Stereocenter Ca • Side Chain • Function • Conformation • Electrical charge

  8. COO- NH3+ H R OH NH2 COOH Amino Acids: Functional Groups • Carboxyl • ACIDIC Ca • BASIC • NEUTRAL • Amine • Amides • Imidazole • Hydroxyl • Guanidino

  9. COO- NH3+ H R Amino Acids: Functional Groups • Carboxyl • ACIDIC Ca • BASIC • NEUTRAL • Amine • Amides • Imidazole • Hydroxyl • Guanidino

  10. Amino Acids: Functional Groups

  11. Amino Acids: Classification

  12. Amino Acids: Classification

  13. Amino Acids: Classification

  14. Amino Acids: Classification

  15. Amino Acids: Classification

  16. H Amino Acids: Ionic State • Titration • Quantitative measure of pKa • Electric charge • Buffering capacity COO H H3N+ Ca R H2N H2O pH = 2 pH = 7 pH = 11 NaOH • Zwitterion • Dipolar ions

  17. COOH COO- COO- NH3+ NH3+ NH2 Ca Ca Ca R R R H H H Amino Acids: Ionic State NaOH NaOH H+ H+ pH = 2 pH = 7 pH = 11 Electric charge = +1 Electric charge = 0 Electric charge = -1 • Zwitterion • Dipolar ions pI pK1 pK2 = + 2

  18. 12 11 10 9 8 pH pK1 pK2 pI = 6.0 7 + 6 2 5 4 3 2 1 0.5 1.0 1.5 Equivalents OH- Titration Curve: Alanine pK2 = 9.7 pK1 = 2.3

  19. NaOH COO- COO- COOH COO- NH3+ NH2 NH3+ NH3+ Ca Ca Ca Ca H H H H H20 RCOOH RCOO- RCOO- RCOOH NaOH H20 NaOH H20 Titration : Glutamic acid 0 +1 pK = 2.2 pK = 4.3 -1 -2 pK = 9.9

  20. COOH COO- COO- NH3+ NH3+ NH2 Ca Ca Ca R R R H H H Titration : Glutamic acid NaOH NaOH H+ H+ pH = 2 pH = 7 pH = 11 Electric charge = +1 Electric charge = 0 Electric charge = -1 • Zwitterion • Dipolar ions pI pK1 pK2 = + 2

  21. 12 11 10 9 8 pK1 pKR pI = 3.25 7 + 6 2 5 4 3 2 1 0.5 1.0 1.5 Titration curve: Glutamic acid pK2 = 9.9 pH pKR = 4.3 pK1 = 2.2 Equivalents OH-

  22. pK Values for Ionizable Groups

  23. Proteins: Structural Organization

  24. R1 O R2 H2N Ca C N Ca COOH H H R1 O R2 H2N Ca C N Ca COOH H H H Peptide bond formation H2 OH + H + H2O

  25. Peptides: Characteristics • Covalent bond : a – amino and a – carboxyl groups • Elimination of H2O • Partial double bond character - C, H, N, and O are co-planar • Trans form is favored

  26. R4 R3 R1 O R2 N Ca COOH N Ca COO H2N Ca C N Ca COO H H H H H H H Peptides: Structural Organization PRIMARY STRUCTURE • DNA - dependent • Sequence of peptide-bonded amino acids • Directionality – NH3 and COOH • Disulfide bonds

  27. R4 R3 R1 O R2 N Ca COO- N Ca COO H2N Ca C N Ca COO H H H H H H H Peptides: Structural Organization SECONDARY STRUCTURE • Arrangement in space • Motifs of hydrogen bonding

  28. Peptides: Structural Organization 2o Sequence • Alpha helix • Beta Pleats Hydrogen bonds

  29. Peptides: Structural Organization TERTIARY STRUCTURE • 3 – dimensional arrangement of atoms • Over-all folding of polypeptide chain • Highest order for monomeric protein

  30. Peptides: Structural Organization QUATERNARY STRUCTURE • Manner of interaction between subunits of multimeric proteins • Domains • Types • Assembly of two proteins that have two different structures • Multiple copies of the same protein

  31. Heirarchy of Protein Structure

  32. SUMMARY • Amino acids are built around an asymmetric a - carbon. • Amino acids are grouped based on similarities of side chain characteristics. • The primary structure of proteins is dictated by genetic information.

  33. Thank you! Please get 1 pc of yellow paper

  34. Differentiate proteins, peptides & amino acids 2. Explain D, L system of configuration 3. Define stereoisomerism; enantiomers 4. Define chirality 5. Define polarity 6. Describe zwitter ion 7. Define R group : relevance 8. Define pKa, pH, pI

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