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Protein Structure

Protein Structure. FDSC400. Biological?. Food?. Protein Functions. Protein Structure. 20 Amino Acids. Coded in DNA. Primary. Secondary. Self assembly to a single (native) structure. Depends on primary structure and solution conditions. Tertiary. ( ). Quaternary.

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Protein Structure

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  1. Protein Structure FDSC400

  2. Biological? Food? Protein Functions

  3. Protein Structure 20 Amino Acids Coded in DNA Primary Secondary Self assembly to a single (native) structure. Depends on primary structure and solution conditions Tertiary ( ) Quaternary Common in foods. Many non-native forms depending on protein structure, solution conditions (& history) and ingredient interactions Denatured

  4. Amino Acids • The monomer unit of proteins • R is the side chain. • One of 20 different chemical compounds • Some R-groups are acid (other alkali) • Some R-groups are water soluble (others are not) Chiral carbon (L-series)

  5. Polar Uncharged. Ser, Thr, Asn, Gln, Cys Positive (basic). Arg, Lys, His Negative (acidic). Asp, Glu, Non-Polar Aliphatic. Ala, Ile, Leu, Met, Pro, Val Aromatic. Phe, Trp, Tyr Amino Acids

  6. Example Amino Acids Alanine Phenylalanine Glutamic acid

  7. Peptide Bonds Amino acids Water

  8. O C N H Peptide Bonds : - O C N H +

  9. Two cysteine molecules under oxidizing conditions Intermolecular or intramolecular cross-link Disulfide Bonds

  10. N-H to C=O hydrogen bonds in 4th succeeding A.A. Hydrogen bonds parallel to axis Typically amphiphilic a-Helix

  11. Amphiphilic 2° Structures Hydrophilic Hydrophobic

  12. C=O and N-H perpendicular to chain form inter-segment H-bonds Parallel or antiparallel b-strands typically 5-15 A.A. More stable than a-helix b-Sheet b-sheet

  13. Protein Folding Hydrophobic amino acids Peptide chain

  14. Tertiary Structure

  15. Types of Tertiary Structure Globular Disordered Fibrous Many insoluble amino acids, protein tends to minimize surface/volume ratio Interacts well with water and takes up a random configuration Strong secondary structure allows protein to retain a non-spherical shape

  16. Quaternary Structure Folded protein unable to contain some hydrophobic residues Dimerized protein shields the hydrophobic amino acids from water

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