1. Protein Structure FDSC400

2. Protein Functions Biological?Food?

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

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. Amino Acids 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

6. Example Amino Acids Alanine Glutamic acid Phenylalanine

7. Peptide Bonds Water Amino acids

8. Peptide Bonds OCNHOCNH OCNHOCNH : - +

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

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

11. Amphiphilic 2° Structures Hydrophilic Hydrophobic

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

13. Hydrophobic amino acids Peptide chain Protein Folding

14. Tertiary Structure

15. Types of Tertiary Structure GlobularDisorderedFibrous 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