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Proteins

Fibrous. Proteins. 1 o structure. amino acid sequence. - helix -sheet. H - bonding between C = O and N - H of backbone. 2 o structure.  +.  -. some proteins only have 1 o and 2 o structure:. fibroin (silk). -sheet. insoluble in H 2 O. hair skin.

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Proteins

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  1. Fibrous Proteins 1o structure amino acid sequence - helix -sheet H-bonding between C=O and N-H of backbone 2o structure + - some proteins only have 1o and 2o structure: fibroin (silk) -sheet insoluble in H2O hair skin - helix keratin collagen non-polar residues

  2. Tertiary structure Primary structure sequence of amino acids Ala-Phe-Ser-Ser-Val-Glu-His-Ile-Met-Arg-Asp-Val-His-Asn-Gly Phe- Ser- Ser- Val- Glu- His- Ile- Met- Arg- Val- His- Asn- Gly- Asp- Ala- Non-polar Polar Acidic or Basic Alanine Serine Glutamic acid Phenylalanine Histidine Arginine Valine Aspartic acid Isoleusine Asperagine Methionine Glycine

  3. 11 4 7 15 Asp Ser His Gly 3 8 Ser Ile Val 14 Asn 12 Arg 10 Ala 1 Glu Val 5 6 Phe Met His 2 9 13 Tertiary structure Ala-Phe-Ser-Ser-Val-Glu-His-Ile-Met-Arg-Asp-Val-His-Asn-Gly arrange these in an -helix polar non-polar interior exterior

  4. - + - - - + + - Tertiary structure interaction of the R-groups globular proteins proteins fold around non-polar groups hydrophobicresidues inside polar and charged residues outside

  5. Tertiary structure interactions of R-groups non-polar R-groups 1. Hydrophobic interactions LDF polar R-groups 2. Hydrogen bonding between H-bond donors and acceptors 3. Ionic bonds (salt bridges) acidic and basic R-groups ion-ion (disulfide) cysteins 4. Covalent bonds

  6. His Ala Phe Arg Asp Cys Cys His CH3 S -O-CH O NH+ = S C-terminus Fe2+ N-terminus Pro Pro

  7. Quaternary Structure subunits hemoglobin 4 - Fe heme groups globin chains 2 -chains 2 - chains held in position by interaction of R-groups polar histidine inside - holds Fe2+ pKa = 6.1

  8. Denaturation form is function denaturation loss of native configuration denaturation peptide bonds not affected H-bonds disulfide bonds ionic bonds L.D.F. disrupted

  9. Denaturation 4o structure disrupted first subunits separate protein unfolds 3o structure disrupted 2o structure disrupted H-bonds broken renatured treatments are sometimes reversible sometimes irreversible insulin

  10. - + - - - + + - SO4- Denaturing treatments above 50-60oC 1. Heat frying egg sunburn 2. pH disrupt salt bridges approach pHI 3. detergents SDS unfold globular proteins Na+

  11. O = _ C O- Denaturing treatments 4. reducing agents S-SSHHS oxidizing agents 5. Metal salts Hg+, Pb+, Ag+ S-Hg Hg+ alcohol acetone 6. H-bonding solvents 7. “Chaotropes” guanidine urea

  12. Words of Wisdom sunburn 1. Heat 6. H-bonding solvents alcohol 3. detergents

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