Non-repeating structures

The secondary structure consists of the local spatial arrangement of the polypeptide chain into repeating structures stabilised by hydrogen bonds, i.e. a-helices and P-sheets. In a-helices, hydrogen bonds are shared by amino acid residues close to each other in the primary sequence of the protein whereas in p-sheets, they involved distant residues. In addition proteins exhibit local non-repeating structures, i.e. turns. 

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