Alpha helix: Difference between revisions

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Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

Karsten Theis, Angel Herraez, Eric Martz

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-The following 4 scenes are inspired by a nice set of figures in Stryer's biochemistry textbook (https://www.ncbi.nlm.nih.gov/books/NBK22580/figure/A322/?report=objectonly). In an alpha helix, the main chain arranges in a <scene name='77/778341/Ribbon/1'>right-handed helix</scene> with the side chains (green) pointing away from the helical axis. The alpha helix is stabilized by <scene name='77/778341/Hbonds/1'>hydrogen bonds</scene> from amino acid n to n+4. There are <scene name='77/778341/Wheel/1'>3.6 residues per turn</scene>. In space filling depiction, you can see how <scene name='77/778341/Space/1'>tightly packed</scene> the main chain is (no space in the middle).
+The following 4 scenes are inspired by a nice set of figures in Stryer's biochemistry textbook (https://www.ncbi.nlm.nih.gov/books/NBK22580/figure/A322/?report=objectonly). In an alpha helix, the main chain arranges in a <scene name='77/778341/Ribbon/1'>right-handed helix</scene> with the side chains (green) pointing away from the helical axis. The alpha helix is stabilized by <scene name='77/778341/Hbonds/2'>hydrogen bonds</scene> from amino acid n to n+4. There are <scene name='77/778341/Wheel/1'>3.6 residues per turn</scene>. In space filling depiction, you can see how <scene name='77/778341/Space/1'>tightly packed</scene> the main chain is (no space in the middle).
-Which amino acids are found in alpha helices?
+==Which amino acids are found in alpha helices?==
-Proline is a helix breaker because its main chain nitrogen is not available for hydrogen bonding.
+Proline is a helix breaker because its main chain nitrogen is not available for hydrogen bonding. Amino acid side chains whose movement is largely restricted in an alpha helix (branched at beta carbon like threonine or valine) are disfavored, as is glycine. Here is an example of a <scene name='77/778341/Proline/1'>kink in a helix</scene> at the position of a proline.