1 / 16

Amino acids

Amino acids. R-groups. non-polar polar acidic basic. proteins. condensation between carboxylic acids and amines. +. +. H 2 O. carboxylic acid. amide. amine. Amides. resonance structure. amides. dipeptide. glycine. alanine. Ala-Gly. +H 2 O. H. H. H. _. _. _. =. =.

abbot-sanders
Download Presentation

Amino acids

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Amino acids R-groups non-polar polar acidic basic proteins condensation between carboxylic acids and amines + + H2O carboxylic acid amide amine

  2. Amides resonance structure amides dipeptide glycine alanine Ala-Gly +H2O

  3. H H H _ _ _ = = = O O O R R R _ _ _ Polypeptides “backbone” _ H N1- C1- C1- N2- C2- C2- N3- C3- C3- OH peptide bonds C-terminal residue N-terminal residue biological activity = structure 4 levels protein structure

  4. Primary structure sequence of amino acids hemoglobin transports O2 and CO2 300 amino acids 4 protein chains Sickle cell anemia 6thamino acid from N-terminus Glu R Val -CH2CH2-CO2H -CH(CH3)2 water soluble water insoluble

  5. H H H _ _ _ _ H N1- C1- C1- N2- C2- C2- N3- C3- C3- OH = = = O O O R R R _ _ _ Secondary structure hydrogen bonding backbone groups H-bond donors H-bond acceptors -helix Two main secondary structures: -sheet

  6. H C N = O C = O Alpha helix Every C=O bonded to N-H 4 residues away forms a helix core is backbone R-groups outside 3.6 amino acids per turn proline no H-bonding breaks helix

  7. Beta sheet Every C=O bonded to N-H far apart in 1o structure on different chains peptide chains extended side-by-side maximal H-bonding for anti-parallel chains small R-groups above and below the sheet if not -helix or -sheet random coil

  8. 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

  9. H H H H C C N N N N C C C C C C S S Disulfide bonds cysteine -CH2-SH S-H H-S reduced [O] oxidized

  10. 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

  11. 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

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

  13. 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

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

  15. - + - - - + + - 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+

  16. 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

More Related