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Unformatted text preview: 2) C-C Torsional Angle (Clockwise rotational) Definitions: Vander-Waals radius radius of an imaginary hard sphere that corresponds to the volume of a particular atom Two atoms cannot occupy positions in space where their separation distance corresponds to a value less than the sum of their Vander Waals radii Two atoms cannot exist in a space where their Vander Waals radii overlap G.N. Ramachandran Built space-filling models to determine the ranges of allowed values of and Ala-Ala-Ala Helical structures proposed by Pauling in 1951 Form when polypeptides are twisted the same amount about each C 11/19/09 -helix 1) = -57 , = =47 2) 3.6 peptides/turn 3)C=O of residue n points directly at NH of residue n+4 4) Van der Waals contact in the helix interior 5) R-groups point outward -pleated sheets -pleated sheets...
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