User:Tilman Schirmer/Sandbox 110

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

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

phi-psi = (-110^o, 130^o), 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 (-140^o, 130^o). See also Ramachandran Plots, http://en.wikipedia.org/wiki/Ramachandran_plot.

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

phi-psi = (-60^o, -40^o), α-helix: ,

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

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