BIOLCHEM 415 1st Edition Lecture 4 Outline of Last Lecture I. Proteins are linear polymers made of 20 different amino acidsII. Amino Acids have different functional propertiesIII. Protein structure: primary, secondary, tertiary, and quaternaryIV. Primary structure: the sequence of amino acidsOutline of Current Lecture V. Hierarchial Protein Structure: primary, secondary, tertiary, quaternaryVI. Secondary structures: α-helices and β-sheetsVII. Protein folding is driven by the hydrophobic effectVIII. Disulfide bonds stabilize protein structureIX. Protein misfolding can contribute to diseasesCurrent LectureSecondary Structure- the Alpha (α) helix- 3.6 residues/turn and 5.4Å/turn- carbonyl and amide groups of peptide bonds are hydrogen bonded- h-bonds between i and i+4 residues- right-handed helix- side chains face outwards- the β sheetThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- each unit is a β-strand- interact with other strands in parallel and antiparallel orientations- C=O h-bonds to N-H in adjacent strands- twisted shape- mixed sheets have both parallel and antiparallel orientationsTertiary Structure- how the secondary elements relate to each other- Myoglobin- completely comprised of α-helices- Fatty acid bonding protein- β-strands (form a β-barrel structure)- some α-helicesDomain- a discrete region in polypeptide chain that folds into an independent unit- usually globular (100-400 amino acids)Quaternary structure- 2 or more polypeptide chains - Cro-protein- dimer with 2 polypeptides- Hemoglobin - tetramer of 2 α subunits and 2 β subunitsProtein Folding- new proteins are unfolded with many different conformations- folded adopt single uniform conformation- powered by hydrophobic effect- hydrophobic amino acids buried in interior of protein- shielded from water- hydrophilic and charged found on the surface (h-bonds)- hydrophobic amino acids inside use van der waalsThermodynamics of Protein Folding- represented by funnel- top = unfolded all possible conformations- molten globule = intermediate- bottom = folded with lowest energyRibonuclease A- disulfide bonds (hydrogen pairs)- not readily denatured- disulfide bonds must be reduced first (denaturate)β-mercaptoethanol- reduces disulfide bonds- new disulfide bonds formed in itselfDiseases caused by protein misfolding- Baline Spongiform Encephalitis and Creutzfeldt-Jacob- prion protein aggregation in neural tissue- death of neurons- formation of amyloid fibers and plaques from neuronal protons - Alzheimer’s and Parkinson’s - neuron
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