Alpha-Helix
Alpha-Helix — A common secondary structure in proteins and peptides where the polypeptide backbone coils into a right-handed helix stabilized by hydrogen bonds.
What Is an Alpha-Helix?
The alpha-helix is the most common secondary structure in peptides and proteins, characterized by a right-handed spiral with 3.6 amino acid residues per turn, a pitch of 5.4 angstroms, and backbone hydrogen bonds between the C=O of residue i and the N-H of residue i+4. It was predicted by Linus Pauling in 1951 and confirmed by X-ray crystallography.
Structural Properties
All amino acid side chains project outward from the helix backbone. Alanine, leucine, methionine, and glutamate are strong helix formers. Proline and glycine are helix breakers. Amphipathic helices (hydrophobic face + hydrophilic face) are the functional motif in antimicrobial peptides and membrane-interacting sequences.
Detection
Circular dichroism shows characteristic double minima at 208 and 222nm. Stapled peptides are specifically designed to lock alpha-helical conformations for protein-protein interaction targeting. Helical content correlates with binding affinity for many helix-mediated interactions.
Frequently Asked Questions
What is Alpha-Helix?
A common secondary structure in proteins and peptides where the polypeptide backbone coils into a right-handed helix stabilized by hydrogen bonds.
Why is Alpha-Helix important in peptide research?
Alpha-Helix is a fundamental concept in structure as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.