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Protein beta-pleated sheets
The beta - pleated sheet is a secondary structure found in proteins in which hydrogen bonds are formed between two parts of the protein chain that can be far apart.
Diagram 1 shows how backbone of the protein is arranged in a sheet. The amino-acids side-chains (lateral groups) are not shown: they would be above and below the plan of the sheet. Hydrogen bonds between the CO and the NH groups are in green on the diagram.
A and B are antiparallel: the two strands are in opposite orientations.
B and C are parallel: the two strands are in the same orientation.
Note: in the case of two antiparallel strands, the hydrogen bonds are parallel to each other, while if two strands are parallel, the hydrogen bonds that link them are not parallel, but oblique.
Diagrams 2 and 3 show two different views of the same beta - pleated sheets rich protein.
In yellow, the parts of the protein involved in the beta - pleated sheets, in pink, some alpha - helices. Random coils are in grey / white.
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