Peptide Secondary Structure
Information on the alpha-helix can be found in your text and lecture notes.
Beta-Turns are usually defined by four amino acids turning back on themselves. The figures below show three of the seven types of beta turns. Note that in each case there is one hydrogen bond and two amino acids at the "corners" of the turns. You should also notice that these structures are all very similar. The difference in confomation is not important at this level. But in biological systems, the correct conformation is the difference between life and death. The type of beta turn displayed is generally related to the identity of the amino acids found in the turn. The use of i, i+1, i+2, and i+3, are symbols used in peptide chemistry to define the first through last residue found in a turn as read from the N-terminus to the C-terminus.
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