2011_10_03_protein_folding1

2011_10_03_protein_folding1 - -early ideas for protein...

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-early ideas for protein folding postulated the existence of templates
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Tertiary structure - Anfinsen (1960) Classic experiment: Ribonuclease A (124 residues with 4 disulfide bonds) 1) remove urea 2) oxidize 100% of activity recovered 1) reoxidize 2) remove urea 1% of activity recovered
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Levinthal’s Paradox Assumption: 3 possible angles for phi and psi Dipeptide: 3x3x3x3 = 3 4 Tripeptide: 3x3x3x3x3x3 = 3 6 Peptide with n residues = 3 2n conformations Peptide with 100 residues = 3 200 ~ 10 100 Singles bonds reorient at a rate of ~10 13 /sec (overestimate) Complete sampling will take 10 100 /10 13 s -1 =10 87 sec Present age of the universe is ~20 billion years = 10 18 sec But proteins can often fold in less than a few seconds! (up to 100 sec)
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polypeptide chain randomly searches through conformations to arrive at native state Golf Course Energy Landscape -horizontal coordinate represents a particular chain conformation - vertical coordinate represents the polypeptide’s internal free energy in a particular conformation
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This note was uploaded on 10/21/2011 for the course BIOC 450 and 45 taught by Professor Various during the Fall '11 term at McGill.

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2011_10_03_protein_folding1 - -early ideas for protein...

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