Alpha helix

Alpha helix is a common protein structure in biochemistry. It is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid located three or four residues earlier along the protein sequence.

Structure

The alpha helix is one of the most common secondary structures in proteins, following the beta sheet. The alpha helix has a cylindrical shape, with the peptide backbone forming the inner part of the cylinder and the side chains extending outward. The alpha helix is tightly packed, with only a small hollow tube running up the middle of the helix.

Stability

The stability of the alpha helix is due to a combination of hydrogen bonds, van der Waals forces, and electrostatic interactions. The hydrogen bonds are formed between the carbonyl oxygen of one amino acid and the amide hydrogen of the amino acid four residues away. This pattern of hydrogen bonding produces a helix with a pitch of 5.4 Å and 3.6 residues per turn.

Role in Proteins

Alpha helices play a crucial role in the structure and function of proteins. They can provide stability to the protein, facilitate binding to other molecules, and participate in enzymatic reactions. Some proteins are almost entirely alpha helical, while others contain only short helical sections.

See Also

• Beta sheet
• Protein structure
• Hydrogen bond
• Van der Waals forces
• Electrostatic interactions

Alpha helix Resources
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