User:Tilman Schirmer/Sandbox 110

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Repetitive torsion angles

A polypeptide chain with a repetition of identical phi-psi torsion angles yields a helical structure.


phi-psi = (180o, 180o), fully extended chain: , .
Note the unfavorably between the carbonyl oxygen and the Cβ-atom of the next residue.


phi-psi = (-110o, 130o), extended chain: , , ; this is the β-strand conformation found in beta-sheets


Note:

  • polypeptide forms a with side-chains protruding towards alternating (up, down) directions
  • the polypeptide main-chain is as can been seen when looking along the chain
  • the point towards alternate directions

    Also strands with a are allowed, but they occur less frequent. This strand has phi-psi values of (-140o, 130o). See also Ramachandran Plots, http://en.wikipedia.org/wiki/Ramachandran_plot.

    phi-psi = (70o, 180o): , ; note that there are clashes (where?)


    phi-psi = (-60o, -40o), α-helix: ,


    phi-psi = (-50o, -26o), 310 helix: ,


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    Tilman Schirmer

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