BIOL-UA 21 Lecture Notes - Lecture 5: X-Ray Crystallography, Alpha Helix, Beta Sheet
18 Mar 2016
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Document Summary
Hierarchical structures determine protein function (structure = function) Secondary = local folding of polypeptide chain. Quaternary = multiple polypeptide subunits coming together with different levels of organization. Whatever shape the proteins take that will determine the function. Alpha helix = each carbonyl oxygen forms a hydrogen bond with the amide hydrogen of the amino acid four positions later in the sequence. Beta sheet individual beta strands align in a parallel or antiparallel fashion forming hydrogen bonds. The beta turn hydrogen bond between irst and fourth amino acids creates a. 180 degrees turn (not a rigid rule, can be a much later polypeptide) Antiparallel = amino to carboxy and the other direction is carboxy to amino. Beta turn = hydrogen bond between first and fourth amino acids creates a 180 degree turn in polypeptide. Conformation usually (protein folding) in which hydrophobic in, hydrophilic out.
