PROTEIN

PROTEIN

1. peptide bond

   • trans configuration
     • rigid, planar ; other C-N are free

2. secondary structure due to hydrogen bonding

   • alpha helix (can be left/right-handed)
     • highly stablized (figure 4.5)
     • not predominant becaz the extent interactions btw side chains
   • beta sheet
     • predominant : the polypeptide chain is nearly fully extended, hydrogen bonds can be intrachain or interchain
     • parallel; antiparallel figure 4.6
   • bend/hairpin loop
     • internal hydrogen bond btw 4th and 1st amino acid
       • glycine becaz flexible
       • proline becaz cyclic structure
   • loop (extended bend)
     • interchangable w/ bend
   • supersecoondary structure / motifs
     • alpha helix, beta sheets and bends are combined into stable geometrical arrangements
       • favorable by covalent interaction btw side chains
       • must look at figure 4.10
   • fibrous protein : water insoluble
     • collagen (rich in proline)
       • triple helix or super helix held by hydrogen bonding and covalent interaction btw side chain
         • high tensile strength => build for bones, tendons

3. tertiary structure ( functional protein

   • combination of several motifs due to hydrophobic interactions and nonpolar side chains, covalent disulfide bonds
   • central dogma of protein folding : primary sturcture determine the 2nd , 3rd structure
   • pg108-110 not mentioned in slide but got underline; go through if got time

4. quarternery sturcture ( multisubunit of proteins)

   • hemoglobin

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